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Date: Tue, 9 Sep 2008 20:02:01 +0200 From: Christoph Hellwig <hch@....de> To: torvalds@...l.org Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org Subject: [PATCH] update Documentation/filesystems/Locking for 2.6.27 changes In the 2.6.27 circle ->fasync lost the BKL, and the last remaining ->open variant that takes the BKL is also gone. ->get_sb and ->kill_sb didn't have BKL forever, so updated the entries while we're at that. Signed-off-by: Christoph Hellwig <hch@....de> Index: linux-2.6/Documentation/filesystems/Locking =================================================================== --- linux-2.6.orig/Documentation/filesystems/Locking 2008-09-09 19:57:03.000000000 +0200 +++ linux-2.6/Documentation/filesystems/Locking 2008-09-09 19:59:46.000000000 +0200 @@ -144,8 +144,8 @@ prototypes: void (*kill_sb) (struct super_block *); locking rules: may block BKL -get_sb yes yes -kill_sb yes yes +get_sb yes no +kill_sb yes no ->get_sb() returns error or 0 with locked superblock attached to the vfsmount (exclusive on ->s_umount). @@ -409,12 +409,12 @@ ioctl: yes (see below) unlocked_ioctl: no (see below) compat_ioctl: no mmap: no -open: maybe (see below) +open: no flush: no release: no fsync: no (see below) aio_fsync: no -fasync: yes (see below) +fasync: no lock: yes readv: no writev: no @@ -431,13 +431,6 @@ For many filesystems, it is probably saf semaphore. Note some filesystems (i.e. remote ones) provide no protection for i_size so you will need to use the BKL. -->open() locking is in-transit: big lock partially moved into the methods. -The only exception is ->open() in the instances of file_operations that never -end up in ->i_fop/->proc_fops, i.e. ones that belong to character devices -(chrdev_open() takes lock before replacing ->f_op and calling the secondary -method. As soon as we fix the handling of module reference counters all -instances of ->open() will be called without the BKL. - Note: ext2_release() was *the* source of contention on fs-intensive loads and dropping BKL on ->release() helps to get rid of that (we still grab BKL for cases when we close a file that had been opened r/w, but that -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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