linux/include
Miklos Szeredi 4ed5e82fe7 vfs: protect remounting superblock read-only
Currently remouting superblock read-only is racy in a major way.

With the per mount read-only infrastructure it is now possible to
prevent most races, which this patch attempts.

Before starting the remount read-only, iterate through all mounts
belonging to the superblock and if none of them have any pending
writes, set sb->s_readonly_remount.  This indicates that remount is in
progress and no further write requests are allowed.  If the remount
succeeds set MS_RDONLY and reset s_readonly_remount.

If the remounting is unsuccessful just reset s_readonly_remount.
This can result in transient EROFS errors, despite the fact the
remount failed.  Unfortunately hodling off writes is difficult as
remount itself may touch the filesystem (e.g. through load_nls())
which would deadlock.

A later patch deals with delayed writes due to nlink going to zero.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-06 23:20:12 -05:00
..
acpi Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2011-11-07 10:13:52 -08:00
asm-generic consolidate umode_t declarations 2012-01-03 22:55:17 -05:00
crypto crypto: Add a report function pointer to crypto_type 2011-10-21 14:24:03 +02:00
drm drm/radeon/kms: add some new pci ids 2011-12-14 12:29:03 +00:00
keys
linux vfs: protect remounting superblock read-only 2012-01-06 23:20:12 -05:00
math-emu
media Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media 2011-12-20 10:49:39 -08:00
misc
mtd
net ipvs: try also real server with port 0 in backup server 2011-12-31 16:06:29 +01:00
pcmcia
rdma Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband 2011-11-01 10:51:38 -07:00
rxrpc
scsi switch ->is_visible() to returning umode_t 2012-01-03 22:54:55 -05:00
sound switch procfs to umode_t use 2012-01-03 22:54:56 -05:00
target target: remove the unused se_dev_list 2011-12-06 06:00:57 +00:00
trace writeback: show writeback reason with __print_symbolic 2011-12-18 14:20:17 +08:00
video ARM: OMAP: HWMOD: Unify DSS resets for OMAPs 2011-11-08 03:16:13 -07:00
xen Revert "xen/pv-on-hvm kexec: add xs_reset_watches to shutdown watches from old kernel" 2011-12-19 09:30:35 -05:00
Kbuild