From: Ross Zwisler <ross.zwisler@linux.intel.com> To: linux-kernel@vger.kernel.org Cc: Ross Zwisler <ross.zwisler@linux.intel.com>, Alexander Viro <viro@zeniv.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org>, Dan Williams <dan.j.williams@intel.com>, Dave Chinner <david@fromorbit.com>, Jan Kara <jack@suse.com>, Matthew Wilcox <willy@linux.intel.com>, linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org Subject: [PATCH v3 5/5] dax: fix clearing of holes in __dax_pmd_fault() Date: Fri, 22 Jan 2016 14:36:13 -0700 [thread overview] Message-ID: <1453498573-6328-6-git-send-email-ross.zwisler@linux.intel.com> (raw) In-Reply-To: <1453498573-6328-1-git-send-email-ross.zwisler@linux.intel.com> When the user reads from a DAX hole via a mmap we service page faults using zero-filled page cache pages. These zero pages are also placed into the address_space radix tree. When we get our first write for that space, we can allocate a PMD page worth of DAX storage to replace that hole. When this happens we need to unmap the zero pages and remove them from the radix tree. Prior to this patch we were unmapping *all* storage in our PMD's range, which is incorrect because it removed DAX entries as well on non-allocating page faults. Instead, keep track of when get_block() actually gives us storage so that we can be sure to only remove zero pages that were covering holes. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reported-by: Jan Kara <jack@suse.cz> --- fs/dax.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index a2ed009..206650f 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -791,9 +791,9 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, bool write = flags & FAULT_FLAG_WRITE; struct block_device *bdev; pgoff_t size, pgoff; - loff_t lstart, lend; sector_t block; int error, result = 0; + bool alloc = false; /* dax pmd mappings require pfn_t_devmap() */ if (!IS_ENABLED(CONFIG_FS_DAX_PMD)) @@ -831,10 +831,17 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); bh.b_size = PMD_SIZE; - if (get_block(inode, block, &bh, write) != 0) + + if (get_block(inode, block, &bh, 0) != 0) return VM_FAULT_SIGBUS; + + if (!buffer_mapped(&bh) && write) { + if (get_block(inode, block, &bh, 1) != 0) + return VM_FAULT_SIGBUS; + alloc = true; + } + bdev = bh.b_bdev; - i_mmap_lock_read(mapping); /* * If the filesystem isn't willing to tell us the length of a hole, @@ -843,15 +850,20 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, */ if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) { dax_pmd_dbg(&bh, address, "allocated block too small"); - goto fallback; + return VM_FAULT_FALLBACK; + } + + /* + * If we allocated new storage, make sure no process has any + * zero pages covering this hole + */ + if (alloc) { + loff_t lstart = pgoff << PAGE_SHIFT; + loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */ + + truncate_pagecache_range(inode, lstart, lend); } - /* make sure no process has any zero pages covering this hole */ - lstart = pgoff << PAGE_SHIFT; - lend = lstart + PMD_SIZE - 1; /* inclusive */ - i_mmap_unlock_read(mapping); - unmap_mapping_range(mapping, lstart, PMD_SIZE, 0); - truncate_inode_pages_range(mapping, lstart, lend); i_mmap_lock_read(mapping); /* -- 2.5.0
WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler@linux.intel.com> To: linux-kernel@vger.kernel.org Cc: Ross Zwisler <ross.zwisler@linux.intel.com>, Alexander Viro <viro@zeniv.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org>, Dan Williams <dan.j.williams@intel.com>, Dave Chinner <david@fromorbit.com>, Jan Kara <jack@suse.com>, Matthew Wilcox <willy@linux.intel.com>, linux-fsdevel@vger.kernel.org, linux-nvdimm@ml01.01.org Subject: [PATCH v3 5/5] dax: fix clearing of holes in __dax_pmd_fault() Date: Fri, 22 Jan 2016 14:36:13 -0700 [thread overview] Message-ID: <1453498573-6328-6-git-send-email-ross.zwisler@linux.intel.com> (raw) In-Reply-To: <1453498573-6328-1-git-send-email-ross.zwisler@linux.intel.com> When the user reads from a DAX hole via a mmap we service page faults using zero-filled page cache pages. These zero pages are also placed into the address_space radix tree. When we get our first write for that space, we can allocate a PMD page worth of DAX storage to replace that hole. When this happens we need to unmap the zero pages and remove them from the radix tree. Prior to this patch we were unmapping *all* storage in our PMD's range, which is incorrect because it removed DAX entries as well on non-allocating page faults. Instead, keep track of when get_block() actually gives us storage so that we can be sure to only remove zero pages that were covering holes. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reported-by: Jan Kara <jack@suse.cz> --- fs/dax.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index a2ed009..206650f 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -791,9 +791,9 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, bool write = flags & FAULT_FLAG_WRITE; struct block_device *bdev; pgoff_t size, pgoff; - loff_t lstart, lend; sector_t block; int error, result = 0; + bool alloc = false; /* dax pmd mappings require pfn_t_devmap() */ if (!IS_ENABLED(CONFIG_FS_DAX_PMD)) @@ -831,10 +831,17 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); bh.b_size = PMD_SIZE; - if (get_block(inode, block, &bh, write) != 0) + + if (get_block(inode, block, &bh, 0) != 0) return VM_FAULT_SIGBUS; + + if (!buffer_mapped(&bh) && write) { + if (get_block(inode, block, &bh, 1) != 0) + return VM_FAULT_SIGBUS; + alloc = true; + } + bdev = bh.b_bdev; - i_mmap_lock_read(mapping); /* * If the filesystem isn't willing to tell us the length of a hole, @@ -843,15 +850,20 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, */ if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) { dax_pmd_dbg(&bh, address, "allocated block too small"); - goto fallback; + return VM_FAULT_FALLBACK; + } + + /* + * If we allocated new storage, make sure no process has any + * zero pages covering this hole + */ + if (alloc) { + loff_t lstart = pgoff << PAGE_SHIFT; + loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */ + + truncate_pagecache_range(inode, lstart, lend); } - /* make sure no process has any zero pages covering this hole */ - lstart = pgoff << PAGE_SHIFT; - lend = lstart + PMD_SIZE - 1; /* inclusive */ - i_mmap_unlock_read(mapping); - unmap_mapping_range(mapping, lstart, PMD_SIZE, 0); - truncate_inode_pages_range(mapping, lstart, lend); i_mmap_lock_read(mapping); /* -- 2.5.0
next prev parent reply other threads:[~2016-01-22 21:36 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-01-22 21:36 [PATCH v3 0/5] DAX fsync/msync fixes Ross Zwisler 2016-01-22 21:36 ` Ross Zwisler 2016-01-22 21:36 ` [PATCH v3 1/5] dax: never rely on bh.b_dev being set by get_block() Ross Zwisler 2016-01-22 21:36 ` Ross Zwisler 2016-01-22 21:36 ` [PATCH v3 2/5] dax: clear TOWRITE flag after flush is complete Ross Zwisler 2016-01-22 21:36 ` Ross Zwisler 2016-01-22 21:36 ` [PATCH v3 3/5] dax: improve documentation for fsync/msync Ross Zwisler 2016-01-22 21:36 ` Ross Zwisler 2016-01-22 21:36 ` [PATCH v3 4/5] dax: fix PMD handling " Ross Zwisler 2016-01-22 21:36 ` Ross Zwisler 2016-01-22 21:36 ` Ross Zwisler [this message] 2016-01-22 21:36 ` [PATCH v3 5/5] dax: fix clearing of holes in __dax_pmd_fault() Ross Zwisler
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