[PATCH 0/3 v3] xfs, mm: memory allocation improvements

[PATCH 0/3 v3] xfs, mm: memory allocation improvements

[Dave Chinner]

We're slowly trying to move the XFS code closer to the common memory
allocation routines everyone else uses. This patch set addresses a
regression from a previous set of changes (kmem_realloc() removal)
and removes another couple of kmem wrappers from within the XFS
code.

The first patch addresses a regression - using large directory
blocks triggers a warning when calling krealloc() recombine a buffer
split across across two log records into a single contiguous
memory buffer. this results in krealloc() being called to allocate a
64kB buffer with __GFP_NOFAIL being set. This warning is trivially
reproduced by generic/040 and generic/041 when run with 64kB
directory block sizes on a 4kB page size machine.

Log recovery really needs to use kvmalloc() like all the other
"allocate up to 64kB and can't fail" cases in filesystem code (e.g.
for xattrs), but there's no native kvrealloc() function that
provides us with the necessary semantics. So rather than add a new
wrapper, the first patch adds this helper to the common code and
converts XFS to use it for log recovery.

The latter two patches are removing what are essentially kvmalloc()
wrappers from XFS. With the more widespread use of
memalloc_nofs_save/restore(), we can call kvmalloc(GFP_KERNEL) and
just have it do the right thing because GFP_NOFS contexts are
covered by PF_MEMALLOC_NOFS task flags now. Hence we don't need
kmem_alloc_large() anymore. And with the slab code guaranteeing at
least 512 byte alignment for sector and block sized heap
allocations, we no longer need the kmem_alloc_io() variant of
kmem_alloc_large() for IO buffers. So these wrappers can all go
away...

Version 3:
- rebase on v5.14-rc1
- handle kvrealloc() failure in xlog_recover_add_to_cont_trans()

Version 2:
- https://lore.kernel.org/linux-xfs/20210630061431.1750745-1-david@fromorbit.com/
- rebase on v5.13 + xfs/for-next
- moved kvrealloc() to mm/util.c
- made incoming pointer const void *
- added null check for vmalloc() failure
- removed xfs_buftarg_dma_alignment()

Original:
- https://lore.kernel.org/linux-xfs/20210625023029.1472466-1-david@fromorbit.com/

[PATCH 1/3] mm: Add kvrealloc()

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

During log recovery of an XFS filesystem with 64kB directory
buffers, rebuilding a buffer split across two log records results
in a memory allocation warning from krealloc like this:

xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
XFS (dm-0): Unmounting Filesystem
XFS (dm-0): Mounting V5 Filesystem
XFS (dm-0): Starting recovery (logdev: internal)
------------[ cut here ]------------
WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
.....
RIP: 0010:get_page_from_freelist+0xdee/0xe40
Call Trace:
 ? complete+0x3f/0x50
 __alloc_pages+0x16f/0x300
 alloc_pages+0x87/0x110
 kmalloc_order+0x2c/0x90
 kmalloc_order_trace+0x1d/0x90
 __kmalloc_track_caller+0x215/0x270
 ? xlog_recover_add_to_cont_trans+0x63/0x1f0
 krealloc+0x54/0xb0
 xlog_recover_add_to_cont_trans+0x63/0x1f0
 xlog_recovery_process_trans+0xc1/0xd0
 xlog_recover_process_ophdr+0x86/0x130
 xlog_recover_process_data+0x9f/0x160
 xlog_recover_process+0xa2/0x120
 xlog_do_recovery_pass+0x40b/0x7d0
 ? __irq_work_queue_local+0x4f/0x60
 ? irq_work_queue+0x3a/0x50
 xlog_do_log_recovery+0x70/0x150
 xlog_do_recover+0x38/0x1d0
 xlog_recover+0xd8/0x170
 xfs_log_mount+0x181/0x300
 xfs_mountfs+0x4a1/0x9b0
 xfs_fs_fill_super+0x3c0/0x7b0
 get_tree_bdev+0x171/0x270
 ? suffix_kstrtoint.constprop.0+0xf0/0xf0
 xfs_fs_get_tree+0x15/0x20
 vfs_get_tree+0x24/0xc0
 path_mount+0x2f5/0xaf0
 __x64_sys_mount+0x108/0x140
 do_syscall_64+0x3a/0x70
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Essentially, we are taking a multi-order allocation from kmem_alloc()
(which has an open coded no fail, no warn loop) and then
reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
then triggering the above warning.

This is a regression caused by converting this code from an open
coded no fail/no warn reallocation loop to using __GFP_NOFAIL.

What we actually need here is kvrealloc(), so that if contiguous
page allocation fails we fall back to vmalloc() and we don't
get nasty warnings happening in XFS.

Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_log_recover.c |  4 +++-
 include/linux/mm.h       |  2 ++
 mm/util.c                | 15 +++++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 1721fce2ec94..3c08d495844d 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2062,7 +2062,9 @@ xlog_recover_add_to_cont_trans(
 	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
 	old_len = item->ri_buf[item->ri_cnt-1].i_len;
 
-	ptr = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);
+	ptr = kvrealloc(old_ptr, old_len, len + old_len, GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
 	memcpy(&ptr[old_len], dp, len);
 	item->ri_buf[item->ri_cnt-1].i_len += len;
 	item->ri_buf[item->ri_cnt-1].i_addr = ptr;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 57453dba41b9..ff9c00bfb76d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -829,6 +829,8 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
 	return kvmalloc_array(n, size, flags | __GFP_ZERO);
 }
 
+extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize,
+		gfp_t flags);
 extern void kvfree(const void *addr);
 extern void kvfree_sensitive(const void *addr, size_t len);
 
diff --git a/mm/util.c b/mm/util.c
index 99c6cc77de9e..b7698d6b2226 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -635,6 +635,21 @@ void kvfree_sensitive(const void *addr, size_t len)
 }
 EXPORT_SYMBOL(kvfree_sensitive);
 
+void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
+{
+	void *newp;
+
+	if (oldsize >= newsize)
+		return (void *)p;
+	newp = kvmalloc(newsize, flags);
+	if (!newp)
+		return NULL;
+	memcpy(newp, p, oldsize);
+	kvfree(p);
+	return newp;
+}
+EXPORT_SYMBOL(kvrealloc);
+
 static inline void *__page_rmapping(struct page *page)
 {
 	unsigned long mapping;
-- 
2.31.1

Re: [PATCH 1/3] mm: Add kvrealloc()

[Mel Gorman]

On Wed, Jul 14, 2021 at 12:34:38PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> During log recovery of an XFS filesystem with 64kB directory
> buffers, rebuilding a buffer split across two log records results
> in a memory allocation warning from krealloc like this:
> 
> xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
> XFS (dm-0): Unmounting Filesystem
> XFS (dm-0): Mounting V5 Filesystem
> XFS (dm-0): Starting recovery (logdev: internal)
> ------------[ cut here ]------------
> WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
> .....
> RIP: 0010:get_page_from_freelist+0xdee/0xe40
> Call Trace:
>  ? complete+0x3f/0x50
>  __alloc_pages+0x16f/0x300
>  alloc_pages+0x87/0x110
>  kmalloc_order+0x2c/0x90
>  kmalloc_order_trace+0x1d/0x90
>  __kmalloc_track_caller+0x215/0x270
>  ? xlog_recover_add_to_cont_trans+0x63/0x1f0
>  krealloc+0x54/0xb0
>  xlog_recover_add_to_cont_trans+0x63/0x1f0
>  xlog_recovery_process_trans+0xc1/0xd0
>  xlog_recover_process_ophdr+0x86/0x130
>  xlog_recover_process_data+0x9f/0x160
>  xlog_recover_process+0xa2/0x120
>  xlog_do_recovery_pass+0x40b/0x7d0
>  ? __irq_work_queue_local+0x4f/0x60
>  ? irq_work_queue+0x3a/0x50
>  xlog_do_log_recovery+0x70/0x150
>  xlog_do_recover+0x38/0x1d0
>  xlog_recover+0xd8/0x170
>  xfs_log_mount+0x181/0x300
>  xfs_mountfs+0x4a1/0x9b0
>  xfs_fs_fill_super+0x3c0/0x7b0
>  get_tree_bdev+0x171/0x270
>  ? suffix_kstrtoint.constprop.0+0xf0/0xf0
>  xfs_fs_get_tree+0x15/0x20
>  vfs_get_tree+0x24/0xc0
>  path_mount+0x2f5/0xaf0
>  __x64_sys_mount+0x108/0x140
>  do_syscall_64+0x3a/0x70
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Essentially, we are taking a multi-order allocation from kmem_alloc()
> (which has an open coded no fail, no warn loop) and then
> reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
> then triggering the above warning.
> 
> This is a regression caused by converting this code from an open
> coded no fail/no warn reallocation loop to using __GFP_NOFAIL.
> 
> What we actually need here is kvrealloc(), so that if contiguous
> page allocation fails we fall back to vmalloc() and we don't
> get nasty warnings happening in XFS.
> 
> Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

Acked-by: Mel Gorman <mgorman@techsingularity.net>

-- 
Mel Gorman
SUSE Labs

Re: [PATCH 1/3] mm: Add kvrealloc()

[Darrick J. Wong]

On Wed, Jul 14, 2021 at 12:34:38PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> During log recovery of an XFS filesystem with 64kB directory
> buffers, rebuilding a buffer split across two log records results
> in a memory allocation warning from krealloc like this:
> 
> xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
> XFS (dm-0): Unmounting Filesystem
> XFS (dm-0): Mounting V5 Filesystem
> XFS (dm-0): Starting recovery (logdev: internal)
> ------------[ cut here ]------------
> WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
> .....
> RIP: 0010:get_page_from_freelist+0xdee/0xe40
> Call Trace:
>  ? complete+0x3f/0x50
>  __alloc_pages+0x16f/0x300
>  alloc_pages+0x87/0x110
>  kmalloc_order+0x2c/0x90
>  kmalloc_order_trace+0x1d/0x90
>  __kmalloc_track_caller+0x215/0x270
>  ? xlog_recover_add_to_cont_trans+0x63/0x1f0
>  krealloc+0x54/0xb0
>  xlog_recover_add_to_cont_trans+0x63/0x1f0
>  xlog_recovery_process_trans+0xc1/0xd0
>  xlog_recover_process_ophdr+0x86/0x130
>  xlog_recover_process_data+0x9f/0x160
>  xlog_recover_process+0xa2/0x120
>  xlog_do_recovery_pass+0x40b/0x7d0
>  ? __irq_work_queue_local+0x4f/0x60
>  ? irq_work_queue+0x3a/0x50
>  xlog_do_log_recovery+0x70/0x150
>  xlog_do_recover+0x38/0x1d0
>  xlog_recover+0xd8/0x170
>  xfs_log_mount+0x181/0x300
>  xfs_mountfs+0x4a1/0x9b0
>  xfs_fs_fill_super+0x3c0/0x7b0
>  get_tree_bdev+0x171/0x270
>  ? suffix_kstrtoint.constprop.0+0xf0/0xf0
>  xfs_fs_get_tree+0x15/0x20
>  vfs_get_tree+0x24/0xc0
>  path_mount+0x2f5/0xaf0
>  __x64_sys_mount+0x108/0x140
>  do_syscall_64+0x3a/0x70
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Essentially, we are taking a multi-order allocation from kmem_alloc()
> (which has an open coded no fail, no warn loop) and then
> reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
> then triggering the above warning.
> 
> This is a regression caused by converting this code from an open
> coded no fail/no warn reallocation loop to using __GFP_NOFAIL.
> 
> What we actually need here is kvrealloc(), so that if contiguous
> page allocation fails we fall back to vmalloc() and we don't
> get nasty warnings happening in XFS.
> 
> Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

Looks good now,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/xfs/xfs_log_recover.c |  4 +++-
>  include/linux/mm.h       |  2 ++
>  mm/util.c                | 15 +++++++++++++++
>  3 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 1721fce2ec94..3c08d495844d 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -2062,7 +2062,9 @@ xlog_recover_add_to_cont_trans(
>  	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
>  	old_len = item->ri_buf[item->ri_cnt-1].i_len;
>  
> -	ptr = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);
> +	ptr = kvrealloc(old_ptr, old_len, len + old_len, GFP_KERNEL);
> +	if (!ptr)
> +		return -ENOMEM;
>  	memcpy(&ptr[old_len], dp, len);
>  	item->ri_buf[item->ri_cnt-1].i_len += len;
>  	item->ri_buf[item->ri_cnt-1].i_addr = ptr;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 57453dba41b9..ff9c00bfb76d 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -829,6 +829,8 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
>  	return kvmalloc_array(n, size, flags | __GFP_ZERO);
>  }
>  
> +extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize,
> +		gfp_t flags);
>  extern void kvfree(const void *addr);
>  extern void kvfree_sensitive(const void *addr, size_t len);
>  
> diff --git a/mm/util.c b/mm/util.c
> index 99c6cc77de9e..b7698d6b2226 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -635,6 +635,21 @@ void kvfree_sensitive(const void *addr, size_t len)
>  }
>  EXPORT_SYMBOL(kvfree_sensitive);
>  
> +void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
> +{
> +	void *newp;
> +
> +	if (oldsize >= newsize)
> +		return (void *)p;
> +	newp = kvmalloc(newsize, flags);
> +	if (!newp)
> +		return NULL;
> +	memcpy(newp, p, oldsize);
> +	kvfree(p);
> +	return newp;
> +}
> +EXPORT_SYMBOL(kvrealloc);
> +
>  static inline void *__page_rmapping(struct page *page)
>  {
>  	unsigned long mapping;
> -- 
> 2.31.1
> 

[PATCH 2/3] xfs: remove kmem_alloc_io()

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

Since commit 59bb47985c1d ("mm, sl[aou]b: guarantee natural alignment
for kmalloc(power-of-two)"), the core slab code now guarantees slab
alignment in all situations sufficient for IO purposes (i.e. minimum
of 512 byte alignment of >= 512 byte sized heap allocations) we no
longer need the workaround in the XFS code to provide this
guarantee.

Replace the use of kmem_alloc_io() with kmem_alloc() or
kmem_alloc_large() appropriately, and remove the kmem_alloc_io()
interface altogether.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/kmem.c            | 25 -------------------------
 fs/xfs/kmem.h            |  1 -
 fs/xfs/xfs_buf.c         |  3 +--
 fs/xfs/xfs_buf.h         |  6 ------
 fs/xfs/xfs_log.c         |  3 +--
 fs/xfs/xfs_log_recover.c |  4 +---
 fs/xfs/xfs_trace.h       |  1 -
 7 files changed, 3 insertions(+), 40 deletions(-)

diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c
index e986b95d94c9..3f2979fd2f2b 100644
--- a/fs/xfs/kmem.c
+++ b/fs/xfs/kmem.c
@@ -56,31 +56,6 @@ __kmem_vmalloc(size_t size, xfs_km_flags_t flags)
 	return ptr;
 }
 
-/*
- * Same as kmem_alloc_large, except we guarantee the buffer returned is aligned
- * to the @align_mask. We only guarantee alignment up to page size, we'll clamp
- * alignment at page size if it is larger. vmalloc always returns a PAGE_SIZE
- * aligned region.
- */
-void *
-kmem_alloc_io(size_t size, int align_mask, xfs_km_flags_t flags)
-{
-	void	*ptr;
-
-	trace_kmem_alloc_io(size, flags, _RET_IP_);
-
-	if (WARN_ON_ONCE(align_mask >= PAGE_SIZE))
-		align_mask = PAGE_SIZE - 1;
-
-	ptr = kmem_alloc(size, flags | KM_MAYFAIL);
-	if (ptr) {
-		if (!((uintptr_t)ptr & align_mask))
-			return ptr;
-		kfree(ptr);
-	}
-	return __kmem_vmalloc(size, flags);
-}
-
 void *
 kmem_alloc_large(size_t size, xfs_km_flags_t flags)
 {
diff --git a/fs/xfs/kmem.h b/fs/xfs/kmem.h
index 38007117697e..9ff20047f8b8 100644
--- a/fs/xfs/kmem.h
+++ b/fs/xfs/kmem.h
@@ -57,7 +57,6 @@ kmem_flags_convert(xfs_km_flags_t flags)
 }
 
 extern void *kmem_alloc(size_t, xfs_km_flags_t);
-extern void *kmem_alloc_io(size_t size, int align_mask, xfs_km_flags_t flags);
 extern void *kmem_alloc_large(size_t size, xfs_km_flags_t);
 static inline void  kmem_free(const void *ptr)
 {
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 8ff42b3585e0..a5ef1f9eb622 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -315,7 +315,6 @@ xfs_buf_alloc_kmem(
 	struct xfs_buf	*bp,
 	xfs_buf_flags_t	flags)
 {
-	int		align_mask = xfs_buftarg_dma_alignment(bp->b_target);
 	xfs_km_flags_t	kmflag_mask = KM_NOFS;
 	size_t		size = BBTOB(bp->b_length);
 
@@ -323,7 +322,7 @@ xfs_buf_alloc_kmem(
 	if (!(flags & XBF_READ))
 		kmflag_mask |= KM_ZERO;
 
-	bp->b_addr = kmem_alloc_io(size, align_mask, kmflag_mask);
+	bp->b_addr = kmem_alloc(size, kmflag_mask);
 	if (!bp->b_addr)
 		return -ENOMEM;
 
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 464dc548fa23..cfbe37d73293 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -355,12 +355,6 @@ extern int xfs_setsize_buftarg(struct xfs_buftarg *, unsigned int);
 #define xfs_getsize_buftarg(buftarg)	block_size((buftarg)->bt_bdev)
 #define xfs_readonly_buftarg(buftarg)	bdev_read_only((buftarg)->bt_bdev)
 
-static inline int
-xfs_buftarg_dma_alignment(struct xfs_buftarg *bt)
-{
-	return queue_dma_alignment(bt->bt_bdev->bd_disk->queue);
-}
-
 int xfs_buf_reverify(struct xfs_buf *bp, const struct xfs_buf_ops *ops);
 bool xfs_verify_magic(struct xfs_buf *bp, __be32 dmagic);
 bool xfs_verify_magic16(struct xfs_buf *bp, __be16 dmagic);
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 36fa2650b081..826b3cf5fd72 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1451,7 +1451,6 @@ xlog_alloc_log(
 	 */
 	ASSERT(log->l_iclog_size >= 4096);
 	for (i = 0; i < log->l_iclog_bufs; i++) {
-		int align_mask = xfs_buftarg_dma_alignment(mp->m_logdev_targp);
 		size_t bvec_size = howmany(log->l_iclog_size, PAGE_SIZE) *
 				sizeof(struct bio_vec);
 
@@ -1463,7 +1462,7 @@ xlog_alloc_log(
 		iclog->ic_prev = prev_iclog;
 		prev_iclog = iclog;
 
-		iclog->ic_data = kmem_alloc_io(log->l_iclog_size, align_mask,
+		iclog->ic_data = kmem_alloc_large(log->l_iclog_size,
 						KM_MAYFAIL | KM_ZERO);
 		if (!iclog->ic_data)
 			goto out_free_iclog;
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 3c08d495844d..d55fc7caa227 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -79,8 +79,6 @@ xlog_alloc_buffer(
 	struct xlog	*log,
 	int		nbblks)
 {
-	int align_mask = xfs_buftarg_dma_alignment(log->l_targ);
-
 	/*
 	 * Pass log block 0 since we don't have an addr yet, buffer will be
 	 * verified on read.
@@ -108,7 +106,7 @@ xlog_alloc_buffer(
 	if (nbblks > 1 && log->l_sectBBsize > 1)
 		nbblks += log->l_sectBBsize;
 	nbblks = round_up(nbblks, log->l_sectBBsize);
-	return kmem_alloc_io(BBTOB(nbblks), align_mask, KM_MAYFAIL | KM_ZERO);
+	return kmem_alloc_large(BBTOB(nbblks), KM_MAYFAIL | KM_ZERO);
 }
 
 /*
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index f9d8d605f9b1..6865e838a71b 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -3689,7 +3689,6 @@ DEFINE_EVENT(xfs_kmem_class, name, \
 	TP_PROTO(ssize_t size, int flags, unsigned long caller_ip), \
 	TP_ARGS(size, flags, caller_ip))
 DEFINE_KMEM_EVENT(kmem_alloc);
-DEFINE_KMEM_EVENT(kmem_alloc_io);
 DEFINE_KMEM_EVENT(kmem_alloc_large);
 
 TRACE_EVENT(xfs_check_new_dalign,
-- 
2.31.1

[PATCH 3/3] xfs: replace kmem_alloc_large() with kvmalloc()

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

There is no reason for this wrapper existing anymore. All the places
that use KM_NOFS allocation are within transaction contexts and
hence covered by memalloc_nofs_save/restore contexts. Hence we don't
need any special handling of vmalloc for large IOs anymore and
so special casing this code isn't necessary.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/kmem.c                 | 39 -----------------------------------
 fs/xfs/kmem.h                 |  1 -
 fs/xfs/libxfs/xfs_attr_leaf.c |  2 +-
 fs/xfs/scrub/attr.c           | 14 +++++++------
 fs/xfs/scrub/attr.h           |  3 ---
 fs/xfs/xfs_log.c              |  4 ++--
 fs/xfs/xfs_log_cil.c          | 10 ++++++++-
 fs/xfs/xfs_log_recover.c      |  2 +-
 fs/xfs/xfs_trace.h            |  1 -
 9 files changed, 21 insertions(+), 55 deletions(-)

diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c
index 3f2979fd2f2b..6f49bf39183c 100644
--- a/fs/xfs/kmem.c
+++ b/fs/xfs/kmem.c
@@ -29,42 +29,3 @@ kmem_alloc(size_t size, xfs_km_flags_t flags)
 		congestion_wait(BLK_RW_ASYNC, HZ/50);
 	} while (1);
 }
-
-
-/*
- * __vmalloc() will allocate data pages and auxiliary structures (e.g.
- * pagetables) with GFP_KERNEL, yet we may be under GFP_NOFS context here. Hence
- * we need to tell memory reclaim that we are in such a context via
- * PF_MEMALLOC_NOFS to prevent memory reclaim re-entering the filesystem here
- * and potentially deadlocking.
- */
-static void *
-__kmem_vmalloc(size_t size, xfs_km_flags_t flags)
-{
-	unsigned nofs_flag = 0;
-	void	*ptr;
-	gfp_t	lflags = kmem_flags_convert(flags);
-
-	if (flags & KM_NOFS)
-		nofs_flag = memalloc_nofs_save();
-
-	ptr = __vmalloc(size, lflags);
-
-	if (flags & KM_NOFS)
-		memalloc_nofs_restore(nofs_flag);
-
-	return ptr;
-}
-
-void *
-kmem_alloc_large(size_t size, xfs_km_flags_t flags)
-{
-	void	*ptr;
-
-	trace_kmem_alloc_large(size, flags, _RET_IP_);
-
-	ptr = kmem_alloc(size, flags | KM_MAYFAIL);
-	if (ptr)
-		return ptr;
-	return __kmem_vmalloc(size, flags);
-}
diff --git a/fs/xfs/kmem.h b/fs/xfs/kmem.h
index 9ff20047f8b8..54da6d717a06 100644
--- a/fs/xfs/kmem.h
+++ b/fs/xfs/kmem.h
@@ -57,7 +57,6 @@ kmem_flags_convert(xfs_km_flags_t flags)
 }
 
 extern void *kmem_alloc(size_t, xfs_km_flags_t);
-extern void *kmem_alloc_large(size_t size, xfs_km_flags_t);
 static inline void  kmem_free(const void *ptr)
 {
 	kvfree(ptr);
diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
index b910bd209949..16d64872acc0 100644
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -489,7 +489,7 @@ xfs_attr_copy_value(
 	}
 
 	if (!args->value) {
-		args->value = kmem_alloc_large(valuelen, KM_NOLOCKDEP);
+		args->value = kvmalloc(valuelen, GFP_KERNEL | __GFP_NOLOCKDEP);
 		if (!args->value)
 			return -ENOMEM;
 	}
diff --git a/fs/xfs/scrub/attr.c b/fs/xfs/scrub/attr.c
index 552af0cf8482..6c36af6dbd35 100644
--- a/fs/xfs/scrub/attr.c
+++ b/fs/xfs/scrub/attr.c
@@ -25,11 +25,11 @@
  * reallocating the buffer if necessary.  Buffer contents are not preserved
  * across a reallocation.
  */
-int
+static int
 xchk_setup_xattr_buf(
 	struct xfs_scrub	*sc,
 	size_t			value_size,
-	xfs_km_flags_t		flags)
+	gfp_t			flags)
 {
 	size_t			sz;
 	struct xchk_xattr_buf	*ab = sc->buf;
@@ -57,7 +57,7 @@ xchk_setup_xattr_buf(
 	 * Don't zero the buffer upon allocation to avoid runtime overhead.
 	 * All users must be careful never to read uninitialized contents.
 	 */
-	ab = kmem_alloc_large(sizeof(*ab) + sz, flags);
+	ab = kvmalloc(sizeof(*ab) + sz, flags);
 	if (!ab)
 		return -ENOMEM;
 
@@ -79,7 +79,7 @@ xchk_setup_xattr(
 	 * without the inode lock held, which means we can sleep.
 	 */
 	if (sc->flags & XCHK_TRY_HARDER) {
-		error = xchk_setup_xattr_buf(sc, XATTR_SIZE_MAX, 0);
+		error = xchk_setup_xattr_buf(sc, XATTR_SIZE_MAX, GFP_KERNEL);
 		if (error)
 			return error;
 	}
@@ -138,7 +138,8 @@ xchk_xattr_listent(
 	 * doesn't work, we overload the seen_enough variable to convey
 	 * the error message back to the main scrub function.
 	 */
-	error = xchk_setup_xattr_buf(sx->sc, valuelen, KM_MAYFAIL);
+	error = xchk_setup_xattr_buf(sx->sc, valuelen,
+			GFP_KERNEL | __GFP_RETRY_MAYFAIL);
 	if (error == -ENOMEM)
 		error = -EDEADLOCK;
 	if (error) {
@@ -323,7 +324,8 @@ xchk_xattr_block(
 		return 0;
 
 	/* Allocate memory for block usage checking. */
-	error = xchk_setup_xattr_buf(ds->sc, 0, KM_MAYFAIL);
+	error = xchk_setup_xattr_buf(ds->sc, 0,
+			GFP_KERNEL | __GFP_RETRY_MAYFAIL);
 	if (error == -ENOMEM)
 		return -EDEADLOCK;
 	if (error)
diff --git a/fs/xfs/scrub/attr.h b/fs/xfs/scrub/attr.h
index 13a1d2e8424d..1719e1c4da59 100644
--- a/fs/xfs/scrub/attr.h
+++ b/fs/xfs/scrub/attr.h
@@ -65,7 +65,4 @@ xchk_xattr_dstmap(
 			BITS_TO_LONGS(sc->mp->m_attr_geo->blksize);
 }
 
-int xchk_setup_xattr_buf(struct xfs_scrub *sc, size_t value_size,
-		xfs_km_flags_t flags);
-
 #endif	/* __XFS_SCRUB_ATTR_H__ */
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 826b3cf5fd72..ec3668508acf 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1462,8 +1462,8 @@ xlog_alloc_log(
 		iclog->ic_prev = prev_iclog;
 		prev_iclog = iclog;
 
-		iclog->ic_data = kmem_alloc_large(log->l_iclog_size,
-						KM_MAYFAIL | KM_ZERO);
+		iclog->ic_data = kvzalloc(log->l_iclog_size,
+				GFP_KERNEL | __GFP_RETRY_MAYFAIL);
 		if (!iclog->ic_data)
 			goto out_free_iclog;
 #ifdef DEBUG
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index b128aaa9b870..d162e8b83e90 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -185,7 +185,15 @@ xlog_cil_alloc_shadow_bufs(
 			 */
 			kmem_free(lip->li_lv_shadow);
 
-			lv = kmem_alloc_large(buf_size, KM_NOFS);
+			/*
+			 * We are in transaction context, which means this
+			 * allocation will pick up GFP_NOFS from the
+			 * memalloc_nofs_save/restore context the transaction
+			 * holds. This means we can use GFP_KERNEL here so the
+			 * generic kvmalloc() code will run vmalloc on
+			 * contiguous page allocation failure as we require.
+			 */
+			lv = kvmalloc(buf_size, GFP_KERNEL);
 			memset(lv, 0, xlog_cil_iovec_space(niovecs));
 
 			lv->lv_item = lip;
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index d55fc7caa227..16df33f838cc 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -106,7 +106,7 @@ xlog_alloc_buffer(
 	if (nbblks > 1 && log->l_sectBBsize > 1)
 		nbblks += log->l_sectBBsize;
 	nbblks = round_up(nbblks, log->l_sectBBsize);
-	return kmem_alloc_large(BBTOB(nbblks), KM_MAYFAIL | KM_ZERO);
+	return kvzalloc(BBTOB(nbblks), GFP_KERNEL | __GFP_RETRY_MAYFAIL);
 }
 
 /*
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 6865e838a71b..38f2f67303f7 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -3689,7 +3689,6 @@ DEFINE_EVENT(xfs_kmem_class, name, \
 	TP_PROTO(ssize_t size, int flags, unsigned long caller_ip), \
 	TP_ARGS(size, flags, caller_ip))
 DEFINE_KMEM_EVENT(kmem_alloc);
-DEFINE_KMEM_EVENT(kmem_alloc_large);
 
 TRACE_EVENT(xfs_check_new_dalign,
 	TP_PROTO(struct xfs_mount *mp, int new_dalign, xfs_ino_t calc_rootino),
-- 
2.31.1

[PATCH 0/3 v2] mm, xfs: memory allocation improvements

[Dave Chinner]

HI folks,

This is an updated version of the patch series first posted here:

https://lore.kernel.org/linux-xfs/20210625023029.1472466-1-david@fromorbit.com/

Changes in this version can be found in the changelog below.

Cheers,

Dave.

-----

We're slowly trying to move the XFS code closer to the common memory
allocation routines everyone else uses. This patch set addresses a
regression from a previous set of changes (kmem_realloc() removal)
and removes another couple of kmem wrappers from within the XFS
code.

The first patch addresses a regression - using large directory
blocks triggers a warning when calling krealloc() recombine a buffer
split across across two log records into a single contiguous
memory buffer. this results in krealloc() being called to allocate a
64kB buffer with __GFP_NOFAIL being set. This warning is trivially
reproduced by generic/040 and generic/041 when run with 64kB
directory block sizes on a 4kB page size machine.

Log recovery really needs to use kvmalloc() like all the other
"allocate up to 64kB and can't fail" cases in filesystem code (e.g.
for xattrs), but there's no native kvrealloc() function that
provides us with the necessary semantics. So rather than add a new
wrapper, the first patch adds this helper to the common code and
converts XFS to use it for log recovery.

The latter two patches are removing what are essentially kvmalloc()
wrappers from XFS. With the more widespread use of
memalloc_nofs_save/restore(), we can call kvmalloc(GFP_KERNEL) and
just have it do the right thing because GFP_NOFS contexts are
covered by PF_MEMALLOC_NOFS task flags now. Hence we don't need
kmem_alloc_large() anymore. And with the slab code guaranteeing at
least 512 byte alignment for sector and block sized heap
allocations, we no longer need the kmem_alloc_io() variant of
kmem_alloc_large() for IO buffers. So these wrappers can all go
away...

Version 2:
- move kvrealloc to mm/util.c
- check for null being returned by vmalloc
- remove unused xfs_buftarg_dma_alignment()

[PATCH 1/3] mm: Add kvrealloc()

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

During log recovery of an XFS filesystem with 64kB directory
buffers, rebuilding a buffer split across two log records results
in a memory allocation warning from krealloc like this:

xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
XFS (dm-0): Unmounting Filesystem
XFS (dm-0): Mounting V5 Filesystem
XFS (dm-0): Starting recovery (logdev: internal)
------------[ cut here ]------------
WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
.....
RIP: 0010:get_page_from_freelist+0xdee/0xe40
Call Trace:
 ? complete+0x3f/0x50
 __alloc_pages+0x16f/0x300
 alloc_pages+0x87/0x110
 kmalloc_order+0x2c/0x90
 kmalloc_order_trace+0x1d/0x90
 __kmalloc_track_caller+0x215/0x270
 ? xlog_recover_add_to_cont_trans+0x63/0x1f0
 krealloc+0x54/0xb0
 xlog_recover_add_to_cont_trans+0x63/0x1f0
 xlog_recovery_process_trans+0xc1/0xd0
 xlog_recover_process_ophdr+0x86/0x130
 xlog_recover_process_data+0x9f/0x160
 xlog_recover_process+0xa2/0x120
 xlog_do_recovery_pass+0x40b/0x7d0
 ? __irq_work_queue_local+0x4f/0x60
 ? irq_work_queue+0x3a/0x50
 xlog_do_log_recovery+0x70/0x150
 xlog_do_recover+0x38/0x1d0
 xlog_recover+0xd8/0x170
 xfs_log_mount+0x181/0x300
 xfs_mountfs+0x4a1/0x9b0
 xfs_fs_fill_super+0x3c0/0x7b0
 get_tree_bdev+0x171/0x270
 ? suffix_kstrtoint.constprop.0+0xf0/0xf0
 xfs_fs_get_tree+0x15/0x20
 vfs_get_tree+0x24/0xc0
 path_mount+0x2f5/0xaf0
 __x64_sys_mount+0x108/0x140
 do_syscall_64+0x3a/0x70
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Essentially, we are taking a multi-order allocation from kmem_alloc()
(which has an open coded no fail, no warn loop) and then
reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
then triggering the above warning.

This is a regression caused by converting this code from an open
coded no fail/no warn reallocation loop to using __GFP_NOFAIL.

What we actually need here is kvrealloc(), so that if contiguous
page allocation fails we fall back to vmalloc() and we don't
get nasty warnings happening in XFS.

Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_log_recover.c |  2 +-
 include/linux/mm.h       |  2 ++
 mm/util.c                | 15 +++++++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 1721fce2ec94..fee4fbadea0a 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2062,7 +2062,7 @@ xlog_recover_add_to_cont_trans(
 	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
 	old_len = item->ri_buf[item->ri_cnt-1].i_len;
 
-	ptr = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);
+	ptr = kvrealloc(old_ptr, old_len, len + old_len, GFP_KERNEL);
 	memcpy(&ptr[old_len], dp, len);
 	item->ri_buf[item->ri_cnt-1].i_len += len;
 	item->ri_buf[item->ri_cnt-1].i_addr = ptr;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8ae31622deef..aa720bc0a1d0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -827,6 +827,8 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
 	return kvmalloc_array(n, size, flags | __GFP_ZERO);
 }
 
+extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize,
+		gfp_t flags);
 extern void kvfree(const void *addr);
 extern void kvfree_sensitive(const void *addr, size_t len);
 
diff --git a/mm/util.c b/mm/util.c
index a8bf17f18a81..1104339ad2ca 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -635,6 +635,21 @@ void kvfree_sensitive(const void *addr, size_t len)
 }
 EXPORT_SYMBOL(kvfree_sensitive);
 
+void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
+{
+	void *newp;
+
+	if (oldsize >= newsize)
+		return (void *)p;
+	newp = kvmalloc(newsize, flags);
+	if (!newp)
+		return NULL;
+	memcpy(newp, p, oldsize);
+	kvfree(p);
+	return newp;
+}
+EXPORT_SYMBOL(kvrealloc);
+
 static inline void *__page_rmapping(struct page *page)
 {
 	unsigned long mapping;
-- 
2.31.1

Re: [PATCH 1/3] mm: Add kvrealloc()

[Mel Gorman]

On Wed, Jun 30, 2021 at 04:14:29PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> During log recovery of an XFS filesystem with 64kB directory
> buffers, rebuilding a buffer split across two log records results
> in a memory allocation warning from krealloc like this:
> 
> xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
> XFS (dm-0): Unmounting Filesystem
> XFS (dm-0): Mounting V5 Filesystem
> XFS (dm-0): Starting recovery (logdev: internal)
> ------------[ cut here ]------------
> WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
> .....
> RIP: 0010:get_page_from_freelist+0xdee/0xe40
> Call Trace:
>  ? complete+0x3f/0x50
>  __alloc_pages+0x16f/0x300
>  alloc_pages+0x87/0x110
>  kmalloc_order+0x2c/0x90
>  kmalloc_order_trace+0x1d/0x90
>  __kmalloc_track_caller+0x215/0x270
>  ? xlog_recover_add_to_cont_trans+0x63/0x1f0
>  krealloc+0x54/0xb0
>  xlog_recover_add_to_cont_trans+0x63/0x1f0
>  xlog_recovery_process_trans+0xc1/0xd0
>  xlog_recover_process_ophdr+0x86/0x130
>  xlog_recover_process_data+0x9f/0x160
>  xlog_recover_process+0xa2/0x120
>  xlog_do_recovery_pass+0x40b/0x7d0
>  ? __irq_work_queue_local+0x4f/0x60
>  ? irq_work_queue+0x3a/0x50
>  xlog_do_log_recovery+0x70/0x150
>  xlog_do_recover+0x38/0x1d0
>  xlog_recover+0xd8/0x170
>  xfs_log_mount+0x181/0x300
>  xfs_mountfs+0x4a1/0x9b0
>  xfs_fs_fill_super+0x3c0/0x7b0
>  get_tree_bdev+0x171/0x270
>  ? suffix_kstrtoint.constprop.0+0xf0/0xf0
>  xfs_fs_get_tree+0x15/0x20
>  vfs_get_tree+0x24/0xc0
>  path_mount+0x2f5/0xaf0
>  __x64_sys_mount+0x108/0x140
>  do_syscall_64+0x3a/0x70
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Essentially, we are taking a multi-order allocation from kmem_alloc()
> (which has an open coded no fail, no warn loop) and then
> reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
> then triggering the above warning.
> 
> This is a regression caused by converting this code from an open
> coded no fail/no warn reallocation loop to using __GFP_NOFAIL.
> 
> What we actually need here is kvrealloc(), so that if contiguous
> page allocation fails we fall back to vmalloc() and we don't
> get nasty warnings happening in XFS.
> 
> Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/xfs_log_recover.c |  2 +-
>  include/linux/mm.h       |  2 ++
>  mm/util.c                | 15 +++++++++++++++
>  3 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 1721fce2ec94..fee4fbadea0a 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -2062,7 +2062,7 @@ xlog_recover_add_to_cont_trans(
>  	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
>  	old_len = item->ri_buf[item->ri_cnt-1].i_len;
>  
> -	ptr = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);
> +	ptr = kvrealloc(old_ptr, old_len, len + old_len, GFP_KERNEL);
>  	memcpy(&ptr[old_len], dp, len);
>  	item->ri_buf[item->ri_cnt-1].i_len += len;
>  	item->ri_buf[item->ri_cnt-1].i_addr = ptr;

While this is an improvement, note that this still potentially fail if,
for example, a vm_struct cannot be allocated for the vmalloc area,
a virtual range is not available, or the pages cannot be allocated
to back the vmalloc range. The last one is potentially problematic if
you look at __vmalloc_node_range and __vmalloc_area_node. vmalloc has
changed a lot since I last familiar with the code but I think it should
not attempt a high-order allocation for 64K but __vmalloc_area_node will
call alloc_pages_node with a GFP mask without __GFP_NOFAIL. In most cases,
it may still succeed but it could fail if the system is OOM. Did I miss
something?

I didn't do a full audit to determine what fallout, if any, there is
to ultimately passing __GFP_NOFAIL to kvmalloc although kvmalloc_node
explicitly notes that __GFP_NOFAIL is not supported. Adding Michal Hocko
to the cc to see if he remembers why __GFP_NOFAIL was problematic.

Absent being able to pass in __GFP_NOFAIL to kvmalloc_node, the new
helper kvrealloc may need to understand __GFP_NOFAIL, avoid passing it
to kvmalloc and indefintiely retry instead to avoid an XFS log recovery
hitting a NULL pointer exception when the memcpy is tried :(

-- 
Mel Gorman
SUSE Labs

Re: [PATCH 1/3] mm: Add kvrealloc()

[Michal Hocko]

On Wed 30-06-21 11:04:55, Mel Gorman wrote:
[...]
> I didn't do a full audit to determine what fallout, if any, there is
> to ultimately passing __GFP_NOFAIL to kvmalloc although kvmalloc_node
> explicitly notes that __GFP_NOFAIL is not supported. Adding Michal Hocko
> to the cc to see if he remembers why __GFP_NOFAIL was problematic.

This is because there are allocations in the vmalloc path which do not
get the full gfp context. E.g. page table allocations. This could be
likely handled somewhere at the vmalloc layer and retry but I do not
remember anybody would be really requesting the support.
-- 
Michal Hocko
SUSE Labs

Re: [PATCH 1/3] mm: Add kvrealloc()

[Darrick J. Wong]

On Wed, Jun 30, 2021 at 04:14:29PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> During log recovery of an XFS filesystem with 64kB directory
> buffers, rebuilding a buffer split across two log records results
> in a memory allocation warning from krealloc like this:
> 
> xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
> XFS (dm-0): Unmounting Filesystem
> XFS (dm-0): Mounting V5 Filesystem
> XFS (dm-0): Starting recovery (logdev: internal)
> ------------[ cut here ]------------
> WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
> .....
> RIP: 0010:get_page_from_freelist+0xdee/0xe40
> Call Trace:
>  ? complete+0x3f/0x50
>  __alloc_pages+0x16f/0x300
>  alloc_pages+0x87/0x110
>  kmalloc_order+0x2c/0x90
>  kmalloc_order_trace+0x1d/0x90
>  __kmalloc_track_caller+0x215/0x270
>  ? xlog_recover_add_to_cont_trans+0x63/0x1f0
>  krealloc+0x54/0xb0
>  xlog_recover_add_to_cont_trans+0x63/0x1f0
>  xlog_recovery_process_trans+0xc1/0xd0
>  xlog_recover_process_ophdr+0x86/0x130
>  xlog_recover_process_data+0x9f/0x160
>  xlog_recover_process+0xa2/0x120
>  xlog_do_recovery_pass+0x40b/0x7d0
>  ? __irq_work_queue_local+0x4f/0x60
>  ? irq_work_queue+0x3a/0x50
>  xlog_do_log_recovery+0x70/0x150
>  xlog_do_recover+0x38/0x1d0
>  xlog_recover+0xd8/0x170
>  xfs_log_mount+0x181/0x300
>  xfs_mountfs+0x4a1/0x9b0
>  xfs_fs_fill_super+0x3c0/0x7b0
>  get_tree_bdev+0x171/0x270
>  ? suffix_kstrtoint.constprop.0+0xf0/0xf0
>  xfs_fs_get_tree+0x15/0x20
>  vfs_get_tree+0x24/0xc0
>  path_mount+0x2f5/0xaf0
>  __x64_sys_mount+0x108/0x140
>  do_syscall_64+0x3a/0x70
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Essentially, we are taking a multi-order allocation from kmem_alloc()
> (which has an open coded no fail, no warn loop) and then
> reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
> then triggering the above warning.
> 
> This is a regression caused by converting this code from an open
> coded no fail/no warn reallocation loop to using __GFP_NOFAIL.
> 
> What we actually need here is kvrealloc(), so that if contiguous
> page allocation fails we fall back to vmalloc() and we don't
> get nasty warnings happening in XFS.
> 
> Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/xfs_log_recover.c |  2 +-
>  include/linux/mm.h       |  2 ++
>  mm/util.c                | 15 +++++++++++++++
>  3 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 1721fce2ec94..fee4fbadea0a 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -2062,7 +2062,7 @@ xlog_recover_add_to_cont_trans(
>  	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
>  	old_len = item->ri_buf[item->ri_cnt-1].i_len;
>  
> -	ptr = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);
> +	ptr = kvrealloc(old_ptr, old_len, len + old_len, GFP_KERNEL);

kvrealloc can return null, so this needs to check for that and -ENOMEM,
right?  It'll suck that log recovery fails, but such is life.

--D

>  	memcpy(&ptr[old_len], dp, len);
>  	item->ri_buf[item->ri_cnt-1].i_len += len;
>  	item->ri_buf[item->ri_cnt-1].i_addr = ptr;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8ae31622deef..aa720bc0a1d0 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -827,6 +827,8 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
>  	return kvmalloc_array(n, size, flags | __GFP_ZERO);
>  }
>  
> +extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize,
> +		gfp_t flags);
>  extern void kvfree(const void *addr);
>  extern void kvfree_sensitive(const void *addr, size_t len);
>  
> diff --git a/mm/util.c b/mm/util.c
> index a8bf17f18a81..1104339ad2ca 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -635,6 +635,21 @@ void kvfree_sensitive(const void *addr, size_t len)
>  }
>  EXPORT_SYMBOL(kvfree_sensitive);
>  
> +void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
> +{
> +	void *newp;
> +
> +	if (oldsize >= newsize)
> +		return (void *)p;
> +	newp = kvmalloc(newsize, flags);
> +	if (!newp)
> +		return NULL;
> +	memcpy(newp, p, oldsize);
> +	kvfree(p);
> +	return newp;
> +}
> +EXPORT_SYMBOL(kvrealloc);
> +
>  static inline void *__page_rmapping(struct page *page)
>  {
>  	unsigned long mapping;
> -- 
> 2.31.1
> 

Re: [PATCH 1/3] mm: Add kvrealloc()

[Dave Chinner]

On Wed, Jun 30, 2021 at 09:08:43AM -0700, Darrick J. Wong wrote:
> On Wed, Jun 30, 2021 at 04:14:29PM +1000, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> > diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> > index 1721fce2ec94..fee4fbadea0a 100644
> > --- a/fs/xfs/xfs_log_recover.c
> > +++ b/fs/xfs/xfs_log_recover.c
> > @@ -2062,7 +2062,7 @@ xlog_recover_add_to_cont_trans(
> >  	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
> >  	old_len = item->ri_buf[item->ri_cnt-1].i_len;
> >  
> > -	ptr = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);
> > +	ptr = kvrealloc(old_ptr, old_len, len + old_len, GFP_KERNEL);
> 
> kvrealloc can return null, so this needs to check for that and -ENOMEM,
> right?  It'll suck that log recovery fails, but such is life.

Ok, looking through the code it seems that returning -ENOMEM here
is a non-destructive (i.e. retry-able) failure. It will simply stop
processing the log at the point this occurs and abort all pending
objects that haven't been processed. The error message is less than
stellar ("log mount/recovery failed: error %d") but at least no
other damage will be done. I'll update it.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

[PATCH 0/3] mm, xfs: memory allocation improvements

[Dave Chinner]

Hi folks,

We're slowly trying to move the XFS code closer to the common memory
allocation routines everyone else uses. This patch set addresses a
regression from a previous set of changes (kmem_realloc() removal)
and removes another couple of kmem wrappers from within the XFS
code.

The first patch addresses a regression - using large directory
blocks triggers a warning when calling krealloc() recombine a buffer
split across across two log records into a single contiguous
memory buffer. this results in krealloc() being called to allocate a
64kB buffer with __GFP_NOFAIL being set. This warning is trivially
reproduced by generic/040 and generic/041 when run with 64kB
directory block sizes on a 4kB page size machine.

Log recovery really needs to use kvmalloc() like all the other
"allocate up to 64kB and can't fail" cases in filesystem code (e.g.
for xattrs), but there's no native kvrealloc() function that
provides us with the necessary semantics. So rather than add a new
wrapper, the first patch adds this helper to the common code and
converts XFS to use it for log recovery.

The latter two patches are removing what are essentially kvmalloc()
wrappers from XFS. With the more widespread use of
memalloc_nofs_save/restore(), we can call kvmalloc(GFP_KERNEL) and
just have it do the right thing because GFP_NOFS contexts are
covered by PF_MEMALLOC_NOFS task flags now. Hence we don't need
kmem_alloc_large() anymore. And with the slab code guaranteeing at
least 512 byte alignment for sector and block sized heap
allocations, we no longer need the kmem_alloc_io() variant of
kmem_alloc_large() for IO buffers. So these wrappers can all go
away...

Cheers,

Dave.

[PATCH 1/3] mm: Add kvrealloc()

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

During log recovery of an XFS filesystem with 64kB directory
buffers, rebuilding a buffer split across two log records results
in a memory allocation warning from krealloc like this:

xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
XFS (dm-0): Unmounting Filesystem
XFS (dm-0): Mounting V5 Filesystem
XFS (dm-0): Starting recovery (logdev: internal)
------------[ cut here ]------------
WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
.....
RIP: 0010:get_page_from_freelist+0xdee/0xe40
Call Trace:
 ? complete+0x3f/0x50
 __alloc_pages+0x16f/0x300
 alloc_pages+0x87/0x110
 kmalloc_order+0x2c/0x90
 kmalloc_order_trace+0x1d/0x90
 __kmalloc_track_caller+0x215/0x270
 ? xlog_recover_add_to_cont_trans+0x63/0x1f0
 krealloc+0x54/0xb0
 xlog_recover_add_to_cont_trans+0x63/0x1f0
 xlog_recovery_process_trans+0xc1/0xd0
 xlog_recover_process_ophdr+0x86/0x130
 xlog_recover_process_data+0x9f/0x160
 xlog_recover_process+0xa2/0x120
 xlog_do_recovery_pass+0x40b/0x7d0
 ? __irq_work_queue_local+0x4f/0x60
 ? irq_work_queue+0x3a/0x50
 xlog_do_log_recovery+0x70/0x150
 xlog_do_recover+0x38/0x1d0
 xlog_recover+0xd8/0x170
 xfs_log_mount+0x181/0x300
 xfs_mountfs+0x4a1/0x9b0
 xfs_fs_fill_super+0x3c0/0x7b0
 get_tree_bdev+0x171/0x270
 ? suffix_kstrtoint.constprop.0+0xf0/0xf0
 xfs_fs_get_tree+0x15/0x20
 vfs_get_tree+0x24/0xc0
 path_mount+0x2f5/0xaf0
 __x64_sys_mount+0x108/0x140
 do_syscall_64+0x3a/0x70
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Essentially, we are taking a multi-order allocation from kmem_alloc()
(which has an open coded no fail, no warn loop) and then
reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
then triggering the above warning.

This is a regression caused by converting this code from an open
coded no fail/no warn reallocation loop to using __GFP_NOFAIL.

What we actually need here is kvrealloc(), so that if contiguous
page allocation fails we fall back to vmalloc() and we don't
get nasty warnings happening in XFS.

Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_log_recover.c |  2 +-
 include/linux/mm.h       | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 1721fce2ec94..fee4fbadea0a 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2062,7 +2062,7 @@ xlog_recover_add_to_cont_trans(
 	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
 	old_len = item->ri_buf[item->ri_cnt-1].i_len;
 
-	ptr = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);
+	ptr = kvrealloc(old_ptr, old_len, len + old_len, GFP_KERNEL);
 	memcpy(&ptr[old_len], dp, len);
 	item->ri_buf[item->ri_cnt-1].i_len += len;
 	item->ri_buf[item->ri_cnt-1].i_addr = ptr;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8ae31622deef..34d88ff00f31 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -830,6 +830,20 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
 extern void kvfree(const void *addr);
 extern void kvfree_sensitive(const void *addr, size_t len);
 
+static inline void *kvrealloc(void *p, size_t oldsize, size_t newsize,
+		gfp_t flags)
+{
+	void *newp;
+
+	if (oldsize >= newsize)
+		return p;
+	newp = kvmalloc(newsize, flags);
+	memcpy(newp, p, oldsize);
+	kvfree(p);
+	return newp;
+}
+
+
 static inline int head_compound_mapcount(struct page *head)
 {
 	return atomic_read(compound_mapcount_ptr(head)) + 1;
-- 
2.31.1

Re: [PATCH 1/3] mm: Add kvrealloc()

[Miaohe Lin]

On 2021/6/25 10:30, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> During log recovery of an XFS filesystem with 64kB directory
> buffers, rebuilding a buffer split across two log records results
> in a memory allocation warning from krealloc like this:
> 
> xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
> XFS (dm-0): Unmounting Filesystem
> XFS (dm-0): Mounting V5 Filesystem
> XFS (dm-0): Starting recovery (logdev: internal)
> ------------[ cut here ]------------
> WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
> .....
> RIP: 0010:get_page_from_freelist+0xdee/0xe40
> Call Trace:
>  ? complete+0x3f/0x50
>  __alloc_pages+0x16f/0x300
>  alloc_pages+0x87/0x110
>  kmalloc_order+0x2c/0x90
>  kmalloc_order_trace+0x1d/0x90
>  __kmalloc_track_caller+0x215/0x270
>  ? xlog_recover_add_to_cont_trans+0x63/0x1f0
>  krealloc+0x54/0xb0
>  xlog_recover_add_to_cont_trans+0x63/0x1f0
>  xlog_recovery_process_trans+0xc1/0xd0
>  xlog_recover_process_ophdr+0x86/0x130
>  xlog_recover_process_data+0x9f/0x160
>  xlog_recover_process+0xa2/0x120
>  xlog_do_recovery_pass+0x40b/0x7d0
>  ? __irq_work_queue_local+0x4f/0x60
>  ? irq_work_queue+0x3a/0x50
>  xlog_do_log_recovery+0x70/0x150
>  xlog_do_recover+0x38/0x1d0
>  xlog_recover+0xd8/0x170
>  xfs_log_mount+0x181/0x300
>  xfs_mountfs+0x4a1/0x9b0
>  xfs_fs_fill_super+0x3c0/0x7b0
>  get_tree_bdev+0x171/0x270
>  ? suffix_kstrtoint.constprop.0+0xf0/0xf0
>  xfs_fs_get_tree+0x15/0x20
>  vfs_get_tree+0x24/0xc0
>  path_mount+0x2f5/0xaf0
>  __x64_sys_mount+0x108/0x140
>  do_syscall_64+0x3a/0x70
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Essentially, we are taking a multi-order allocation from kmem_alloc()
> (which has an open coded no fail, no warn loop) and then
> reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
> then triggering the above warning.
> 
> This is a regression caused by converting this code from an open
> coded no fail/no warn reallocation loop to using __GFP_NOFAIL.
> 
> What we actually need here is kvrealloc(), so that if contiguous
> page allocation fails we fall back to vmalloc() and we don't
> get nasty warnings happening in XFS.
> 
> Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

Thank you for your patch.

> ---
>  fs/xfs/xfs_log_recover.c |  2 +-
>  include/linux/mm.h       | 14 ++++++++++++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 1721fce2ec94..fee4fbadea0a 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -2062,7 +2062,7 @@ xlog_recover_add_to_cont_trans(
>  	old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
>  	old_len = item->ri_buf[item->ri_cnt-1].i_len;
>  
> -	ptr = krealloc(old_ptr, len + old_len, GFP_KERNEL | __GFP_NOFAIL);
> +	ptr = kvrealloc(old_ptr, old_len, len + old_len, GFP_KERNEL);
>  	memcpy(&ptr[old_len], dp, len);
>  	item->ri_buf[item->ri_cnt-1].i_len += len;
>  	item->ri_buf[item->ri_cnt-1].i_addr = ptr;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8ae31622deef..34d88ff00f31 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -830,6 +830,20 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
>  extern void kvfree(const void *addr);
>  extern void kvfree_sensitive(const void *addr, size_t len);
>  
> +static inline void *kvrealloc(void *p, size_t oldsize, size_t newsize,
> +		gfp_t flags)
> +{
> +	void *newp;
> +
> +	if (oldsize >= newsize)
> +		return p;
> +	newp = kvmalloc(newsize, flags);

Shouldn't we check newp against NULL before memcpy?
Thanks.

> +	memcpy(newp, p, oldsize);
> +	kvfree(p);
> +	return newp;
> +}
> +
> +
>  static inline int head_compound_mapcount(struct page *head)
>  {
>  	return atomic_read(compound_mapcount_ptr(head)) + 1;
> 

Re: [PATCH 1/3] mm: Add kvrealloc()

[Dave Chinner]

On Fri, Jun 25, 2021 at 10:40:08AM +0800, Miaohe Lin wrote:
> On 2021/6/25 10:30, Dave Chinner wrote:
> > @@ -830,6 +830,20 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
> >  extern void kvfree(const void *addr);
> >  extern void kvfree_sensitive(const void *addr, size_t len);
> >  
> > +static inline void *kvrealloc(void *p, size_t oldsize, size_t newsize,
> > +		gfp_t flags)
> > +{
> > +	void *newp;
> > +
> > +	if (oldsize >= newsize)
> > +		return p;
> > +	newp = kvmalloc(newsize, flags);
> 
> Shouldn't we check newp against NULL before memcpy?

Sure, the flags cwwe pass it from XFS mean it can't fail, but I
guess someone could add a noretry flag or something like that...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: [PATCH 1/3] mm: Add kvrealloc()

[Matthew Wilcox]

On Fri, Jun 25, 2021 at 12:30:27PM +1000, Dave Chinner wrote:
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8ae31622deef..34d88ff00f31 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -830,6 +830,20 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
>  extern void kvfree(const void *addr);
>  extern void kvfree_sensitive(const void *addr, size_t len);
>  
> +static inline void *kvrealloc(void *p, size_t oldsize, size_t newsize,
> +		gfp_t flags)
> +{
> +	void *newp;
> +
> +	if (oldsize >= newsize)
> +		return p;
> +	newp = kvmalloc(newsize, flags);
> +	memcpy(newp, p, oldsize);
> +	kvfree(p);
> +	return newp;
> +}

Why make this an inline function instead of putting it in mm/util.c?

Re: [PATCH 1/3] mm: Add kvrealloc()

[Dave Chinner]

On Fri, Jun 25, 2021 at 04:54:11AM +0100, Matthew Wilcox wrote:
> On Fri, Jun 25, 2021 at 12:30:27PM +1000, Dave Chinner wrote:
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 8ae31622deef..34d88ff00f31 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -830,6 +830,20 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
> >  extern void kvfree(const void *addr);
> >  extern void kvfree_sensitive(const void *addr, size_t len);
> >  
> > +static inline void *kvrealloc(void *p, size_t oldsize, size_t newsize,
> > +		gfp_t flags)
> > +{
> > +	void *newp;
> > +
> > +	if (oldsize >= newsize)
> > +		return p;
> > +	newp = kvmalloc(newsize, flags);
> > +	memcpy(newp, p, oldsize);
> > +	kvfree(p);
> > +	return newp;
> > +}
> 
> Why make this an inline function instead of putting it in mm/util.c?

Not fussed, I can do that.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com