From: Arnd Bergmann <arnd@arndb.de> To: Nick Piggin <npiggin@gmail.com> Cc: linux-kernel@vger.kernel.org, Nick Bowler <nbowler@elliptictech.com>, Evgeniy Dushistov <dushistov@mail.ru> Subject: Re: [PATCH 15/20] ufs: remove the BKL Date: Thu, 27 Jan 2011 14:13:00 +0100 [thread overview] Message-ID: <201101271413.01204.arnd@arndb.de> (raw) In-Reply-To: <AANLkTinKO=HM1BqDdFkdcCAGz85co64Ma79qomw6PDPp@mail.gmail.com> On Thursday 27 January 2011, Nick Piggin wrote: > On Wed, Jan 26, 2011 at 9:17 AM, Arnd Bergmann <arnd@arndb.de> wrote: > > This introduces a new per-superblock mutex in UFS to replace > > the big kernel lock. I have been careful to avoid nested > > calls to lock_ufs and to get the lock order right with > > respect to other mutexes, in particular lock_super. > > When I looked at removing bkl from minix a long time ago, > I was a bit worried about reclaim and fs/io recursion in some > of the filesystems with bkl. Thanks for looking at this, you certainly understand these interactions much better than me! > > @@ -436,7 +439,8 @@ int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buffer_head > > ret = 0; > > bh = NULL; > > > > - lock_kernel(); > > + if (needs_lock) > > + lock_ufs(sb); > > > > UFSD("ENTER, ino %lu, fragment %llu\n", inode->i_ino, (unsigned long long)fragment); > > if (fragment > > So, get_block can be called for .writepage in page reclaim, > which takes the lock. ufs_lookup takes the lock and winds > up calling ufs_alloc_inode. And ufs_alloc_inode does > GFP_KERNEL, which can enter reclaim with __GFP_FS > set. This is one path that I did not consider. My initial thought when you mentioned it was that this is still fine because ufs_getfrag_block can be called with the lock held by the current task, but you are of course right that this won't work when we are called by the writeback task. > I didn't look through all your filesystem conversions, but it is > something tricky to watch out for I think. The only other one where I added locks is isofs, and I'm pretty sure that's fine because it's read-only and does not do writeback. HPFS with Andi's suggested solution of making it UP-only is of course also fine. > Changing everything to GFP_NOFS may be an option, for > such crufty old filesystems... Yes. All performance optimizations in UFS are pointless anyway as long as we do most of the disk I/O under a global mutex. The patch below converts all allocations that are done under a lock in UFS to GFP_NOFS. If nobody comes up with a better solution, I'll fold that into my other patch. Arnd --- fs/ufs/super.c | 8 ++++---- fs/ufs/util.c | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/fs/ufs/super.c b/fs/ufs/super.c index e4e06ef..7693d62 100644 --- a/fs/ufs/super.c +++ b/fs/ufs/super.c @@ -539,7 +539,7 @@ static int ufs_read_cylinder_structures(struct super_block *sb) */ size = uspi->s_cssize; blks = (size + uspi->s_fsize - 1) >> uspi->s_fshift; - base = space = kmalloc(size, GFP_KERNEL); + base = space = kmalloc(size, GFP_NOFS); if (!base) goto failed; sbi->s_csp = (struct ufs_csum *)space; @@ -564,7 +564,7 @@ static int ufs_read_cylinder_structures(struct super_block *sb) * Read cylinder group (we read only first fragment from block * at this time) and prepare internal data structures for cg caching. */ - if (!(sbi->s_ucg = kmalloc (sizeof(struct buffer_head *) * uspi->s_ncg, GFP_KERNEL))) + if (!(sbi->s_ucg = kmalloc (sizeof(struct buffer_head *) * uspi->s_ncg, GFP_NOFS))) goto failed; for (i = 0; i < uspi->s_ncg; i++) sbi->s_ucg[i] = NULL; @@ -582,7 +582,7 @@ static int ufs_read_cylinder_structures(struct super_block *sb) ufs_print_cylinder_stuff(sb, (struct ufs_cylinder_group *) sbi->s_ucg[i]->b_data); } for (i = 0; i < UFS_MAX_GROUP_LOADED; i++) { - if (!(sbi->s_ucpi[i] = kmalloc (sizeof(struct ufs_cg_private_info), GFP_KERNEL))) + if (!(sbi->s_ucpi[i] = kmalloc (sizeof(struct ufs_cg_private_info), GFP_NOFS))) goto failed; sbi->s_cgno[i] = UFS_CGNO_EMPTY; } @@ -1415,7 +1415,7 @@ static struct kmem_cache * ufs_inode_cachep; static struct inode *ufs_alloc_inode(struct super_block *sb) { struct ufs_inode_info *ei; - ei = (struct ufs_inode_info *)kmem_cache_alloc(ufs_inode_cachep, GFP_KERNEL); + ei = (struct ufs_inode_info *)kmem_cache_alloc(ufs_inode_cachep, GFP_NOFS); if (!ei) return NULL; ei->vfs_inode.i_version = 1; diff --git a/fs/ufs/util.c b/fs/ufs/util.c index d2c36d5..95425b5 100644 --- a/fs/ufs/util.c +++ b/fs/ufs/util.c @@ -27,7 +27,7 @@ struct ufs_buffer_head * _ubh_bread_ (struct ufs_sb_private_info * uspi, if (count > UFS_MAXFRAG) return NULL; ubh = (struct ufs_buffer_head *) - kmalloc (sizeof (struct ufs_buffer_head), GFP_KERNEL); + kmalloc (sizeof (struct ufs_buffer_head), GFP_NOFS); if (!ubh) return NULL; ubh->fragment = fragment;
next prev parent reply other threads:[~2011-01-27 13:13 UTC|newest] Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-01-25 22:17 [RFC 00/20] Proposal for remaining BKL users Arnd Bergmann 2011-01-25 22:17 ` Arnd Bergmann 2011-01-25 22:17 ` [PATCH 01/20] drm/i810: remove the BKL Arnd Bergmann 2011-01-25 22:17 ` [PATCH 02/20] drm: remove i830 driver Arnd Bergmann 2011-01-25 22:17 ` [PATCH 03/20] staging/usbip: convert to kthread Arnd Bergmann 2011-01-28 17:53 ` Max Vozeler 2011-01-28 18:48 ` Arnd Bergmann 2011-03-01 22:15 ` Arnd Bergmann 2011-01-25 22:17 ` [PATCH 04/20] staging/cx25721: serialize access to devlist Arnd Bergmann 2011-01-26 16:23 ` Palash Bandyopadhyay 2011-01-31 21:37 ` Greg KH 2011-01-25 22:17 ` [PATCH 05/20] staging/go7007: remove the BKL Arnd Bergmann 2011-01-25 22:17 ` [PATCH 06/20] staging: Remove autofs3 Arnd Bergmann 2011-01-26 7:41 ` H. Peter Anvin 2011-01-25 22:17 ` [PATCH 07/20] staging: remove smbfs Arnd Bergmann 2011-01-25 22:17 ` [PATCH 08/20] adfs: remove the big kernel lock Arnd Bergmann 2011-01-25 22:20 ` Russell King 2011-01-25 22:17 ` [PATCH 09/20] hpfs: rename big kernel lock to hpfs_lock Arnd Bergmann 2011-01-25 22:17 ` [PATCH 10/20] hpfs: replace BKL with a global mutex Arnd Bergmann 2011-01-26 0:15 ` Andi Kleen 2011-01-26 0:19 ` Andi Kleen 2011-01-26 12:48 ` [PATCH v2] hpfs: remove the BKL Arnd Bergmann 2011-01-26 12:50 ` [PATCH 10/20] hpfs: replace BKL with a global mutex Arnd Bergmann 2011-01-26 16:52 ` Andi Kleen 2011-01-27 5:01 ` Nick Piggin 2011-01-27 10:57 ` Miklos Szeredi 2011-01-25 22:17 ` [PATCH 11/20] hpfs: move to drivers/staging Arnd Bergmann 2011-02-07 16:17 ` Mikulas Patocka 2011-02-07 19:31 ` Arnd Bergmann 2011-01-25 22:17 ` [PATCH 12/20] x25: remove the BKL Arnd Bergmann 2011-01-27 10:07 ` Andrew Hendry 2011-01-27 12:17 ` Arnd Bergmann 2011-01-27 12:38 ` [PATCH v2] " Arnd Bergmann 2011-01-27 13:20 ` Eric Dumazet 2011-01-27 13:43 ` Arnd Bergmann 2011-01-25 22:17 ` [PATCH 13/20] appletalk: move to staging Arnd Bergmann 2011-01-25 22:17 ` [PATCH 14/20] staging/appletalk: remove the BKL Arnd Bergmann 2011-01-25 22:29 ` David Miller 2011-01-26 12:57 ` Arnd Bergmann 2011-01-25 22:17 ` [PATCH 15/20] ufs: " Arnd Bergmann 2011-01-26 2:30 ` Nick Bowler 2011-01-26 12:53 ` Arnd Bergmann 2011-01-27 5:47 ` Nick Piggin 2011-01-27 13:13 ` Arnd Bergmann [this message] 2011-01-25 22:17 ` [PATCH 16/20] ipx: " Arnd Bergmann 2011-01-25 22:17 ` [PATCH 17/20] tracing: don't trace " Arnd Bergmann 2011-01-25 22:28 ` Frederic Weisbecker 2011-01-25 22:17 ` [PATCH 18/20] rtmutex-tester: remove BKL tests Arnd Bergmann 2011-01-26 15:00 ` [tip:core/locking] rtmutex-tester: Remove " tip-bot for Arnd Bergmann 2011-02-22 20:57 ` [tip:irq/core] rtmutex: tester: " tip-bot for Arnd Bergmann 2011-01-25 22:17 ` [PATCH 19/20] drivers: remove extraneous includes of smp_lock.h Arnd Bergmann 2011-01-25 22:17 ` [PATCH 20/20] BKL: That's all, folks Arnd Bergmann 2011-01-26 6:19 ` Ingo Molnar 2011-01-26 8:47 ` Alan Cox 2011-01-26 11:01 ` Ingo Molnar 2011-01-26 11:22 ` Thomas Gleixner 2011-01-26 2:22 ` [RFC 00/20] Proposal for remaining BKL users Greg KH 2011-01-26 2:22 ` Greg KH 2011-01-26 11:31 ` Arnd Bergmann 2011-01-26 11:31 ` Arnd Bergmann 2011-01-26 11:58 ` Mauro Carvalho Chehab 2011-01-26 13:45 ` Arnd Bergmann 2011-01-26 13:45 ` Arnd Bergmann 2011-01-26 16:24 ` Palash Bandyopadhyay
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