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authorNick Piggin <npiggin@kernel.dk>2011-01-07 17:49:54 +1100
committerNick Piggin <npiggin@kernel.dk>2011-01-07 17:50:28 +1100
commit5f57cbcc02cf18f6b22ef4066bb10afeb8f930ff (patch)
treef02e7ee57e6060f0af1bcda281baf2972d2da72f /fs/libfs.c
parentc28cc36469554dc55540f059fbdc7fa22a2c31fc (diff)
downloadlinux-linaro-stable-5f57cbcc02cf18f6b22ef4066bb10afeb8f930ff.tar.gz
fs: dcache remove d_mounted
Rather than keep a d_mounted count in the dentry, set a dentry flag instead. The flag can be cleared by checking the hash table to see if there are any mounts left, which is not time critical because it is performed at detach time. The mounted state of a dentry is only used to speculatively take a look in the mount hash table if it is set -- before following the mount, vfsmount lock is taken and mount re-checked without races. This saves 4 bytes on 32-bit, nothing on 64-bit but it does provide a hole I might use later (and some configs have larger than 32-bit spinlocks which might make use of the hole). Autofs4 conversion and changelog by Ian Kent <raven@themaw.net>: In autofs4, when expring direct (or offset) mounts we need to ensure that we block user path walks into the autofs mount, which is covered by another mount. To do this we clear the mounted status so that follows stop before walking into the mount and are essentially blocked until the expire is completed. The automount daemon still finds the correct dentry for the umount due to the follow mount logic in fs/autofs4/root.c:autofs4_follow_link(), which is set as an inode operation for direct and offset mounts only and is called following the lookup that stopped at the covered mount. At the end of the expire the covering mount probably has gone away so the mounted status need not be restored. But we need to check this and only restore the mounted status if the expire failed. XXX: autofs may not work right if we have other mounts go over the top of it? Signed-off-by: Nick Piggin <npiggin@kernel.dk>
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