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Just nail the oddments now while this code is being touched
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Changelog [v2]:
- Add note indicating strict isolation is not possible unless all
mounts of devpts use the 'newinstance' mount option.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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To support containers, allow multiple instances of devpts filesystem, such
that indices of ptys allocated in one instance are independent of ptys
allocated in other instances of devpts.
But to preserve backward compatibility, enable this support for multiple
instances only if:
- CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and
- '-o newinstance' mount option is specified while mounting devpts
To use multi-instance mount, a container startup script could:
$ ns_exec -cm /bin/bash
$ umount /dev/pts
$ mount -t devpts -o newinstance lxcpts /dev/pts
$ mount -o bind /dev/pts/ptmx /dev/ptmx
$ /usr/sbin/sshd -p 1234
where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs
/bin/bash in the child process. A pty created by the sshd is not visible in
the original mount of /dev/pts.
USER-SPACE-IMPACT:
- See Documentation/fs/devpts.txt (included in next patch) for user-
space impact in multi-instance and mixed-mode operation.
TODO:
- Update mount(8), pts(4) man pages. Highlight impact of not
redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount.
Changelog[v6]:
- [Dave Hansen] Use new get_init_pts_sb() interface
- [Serge Hallyn] Don't bother displaying 'newinstance' in show_options
- [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1.
- [Serge Hallyn] Check error return from get_sb_single() (now
get_init_pts_sb())
- devpts_pty_kill(): don't dput error dentries
Changelog[v5]:
- Move get_sb_ref() definition to earlier patch
- Move usage info to Documentation/filesystems/devpts.txt (next patch)
- Make ptmx node even in init_pts_ns, now that default mode is 0000
(defined in earlier patch, enabled here).
- Cache ptmx dentry and use to update mode during remount
(defined in earlier patch, enabled here).
- Bugfix: explicitly ignore newinstance on remount (if newinstance was
specified on remount of initial mount, it would be ignored but
/proc/mounts would imply that the option was set)
Changelog[v4]:
- Update patch description to address H. Peter Anvin's comments
- Consolidate multi-instance mode code under new config token,
CONFIG_DEVPTS_MULTIPLE_INSTANCE.
- Move usage-details from patch description to
Documentation/fs/devpts.txt
Changelog[v3]:
- Rename new mount option to 'newinstance'
- Create ptmx nodes only in 'newinstance' mounts
- Bugfix: parse_mount_options() modifies @data but since we need to
parse the @data twice (once in devpts_get_sb() and once during
do_remount_sb()), parse a local copy of @data in devpts_get_sb().
(restructured code in devpts_get_sb() to fix this)
Changelog[v2]:
- Support both single-mount and multiple-mount semantics and
provide '-onewmnt' option to select the semantics.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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See comments in the function header for details. The new interface will
be used in a follow-on patch.
Changelog [v2]:
[Dave Hansen] Replace get_sb_ref() in fs/super.c with get_init_pts_sb()
and make the new interface private to devpts
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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/dev/ptmx is closely tied to the devpts filesystem. An open of /dev/ptmx,
allocates the next pty index and the associated device shows up in the
devpts fs as /dev/pts/n.
Wih multiple instancs of devpts filesystem, during an open of /dev/ptmx
we would be unable to determine which instance of the devpts is being
accessed.
So we move the 'ptmx' node into /dev/pts and use the inode of the 'ptmx'
node to identify the superblock and hence the devpts instance. This patch
adds ability for the kernel to internally create the [ptmx, c, 5:2] device
when mounting devpts filesystem. Since the ptmx node in devpts is new and
may surprise some userspace scripts, the default permissions for the new
node is 0000. These permissions can be changed either using chmod or by
remounting with the new '-o ptmxmode=0666' mount option.
Changelog[v5]:
- [Serge Hallyn bugfix]: Letting new_inode() assign inode number to
ptmx can collide with hand-assigning inode numbers to ptys. So,
hand-assign specific inode number to ptmx node also.
- [Serge Hallyn]: Maybe safer to grab root dentry mutex while creating
ptmx node
- [Bugfix with Serge Hallyn] Replace lookup_one_len() in mknod_ptmx()
wih d_alloc_name() (lookup during ->get_sb() locks up system). To
simplify patchset, fold the ptmx_dentry patch into this.
Changelog[v4]:
- Change default permissions of pts/ptmx node to 0000.
- Move code for ptmxmode under #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES.
Changelog[v3]:
- Rename ptmx_mode to ptmxmode (for consistency with 'newinstance')
Changelog[v2]:
- [H. Peter Anvin] Remove mknod() system call support and create the
ptmx node internally.
Changelog[v1]:
- Earlier version of this patch enabled creating /dev/pts/tty as
well. As pointed out by Al Viro and H. Peter Anvin, that is not
really necessary.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Move code to parse mount options into a separate function so it can
(later) be shared between mount and remount operations.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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With support for multiple mounts of devpts, the 'config' structure really
represents per-mount options rather than config parameters. Rename 'config'
structure to 'pts_mount_opts' and store it in the super-block.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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To enable multiple mounts of devpts, 'allocated_ptys' must be a per-mount
variable rather than a global variable. Move 'allocated_ptys' into the
super_block's s_fs_info.
Changelog[v2]:
Define and use DEVPTS_SB() wrapper.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Remove the 'devpts_root' global variable and find the root dentry using
the super_block. The super-block can be found from the device inode, using
the new wrapper, pts_sb_from_inode().
Changelog: This patch is based on an earlier patchset from Serge Hallyn
and Matt Helsley.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Now the main work is done its polishing time
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Fixes the loss of echoed (and other ldisc-generated characters) when
the tty is stopped or when the driver output buffer is full (happens
frequently for input during continuous program output, such as ^C)
and removes the Big Kernel Lock from the N_TTY line discipline.
Adds an "echo buffer" to the N_TTY line discipline that handles all
ldisc-generated output (including echoed characters). Along with the
loss of characters, this also fixes the associated loss of sync between
tty output and the ldisc state when characters cannot be immediately
written to the tty driver.
The echo buffer stores (in addition to characters) state operations that need
to be done at the time of character output (like management of the column
position). This allows echo to cooperate correctly with program output,
since the ldisc state remains consistent with actual characters written.
Since the echo buffer code now isolates the tty column state code
to the process_out* and process_echoes functions, we can remove the
Big Kernel Lock (BKL) and replace it with mutex locks.
Highlights are:
* Handles echo (and other ldisc output) when tty driver buffer is full
- continuous program output can block echo
* Saves echo when tty is in stopped state (e.g. ^S)
- (e.g.: ^Q will correctly cause held characters to be released for output)
* Control character pairs (e.g. "^C") are treated atomically and not
split up by interleaved program output
* Line discipline state is kept consistent with characters sent to
the tty driver
* Remove the big kernel lock (BKL) from N_TTY line discipline
Signed-off-by: Joe Peterson <joe@skyrush.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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over UART in DMA mode
Add spin_lock_irqsave() when receive and transfer data.
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Bug description:
The IRDA receiver may can't receiving any more after processed some signals.
To duplicate this issue is put three IRDA devices together, one blackfin,
two none blackfin, they will detect each other. Let one none blackfin devices
irdaping the blackfin devices, when it stopped print out ping information,
it is the time that blackfin stoped receiving, the time is random.
The related register bit is OK, the other devices is sending data continuously.
But no interrupt come.
Fixing:
I tried Michael's suggestion that request the UARTx error interrupt, and reset
the IRDA when found FE error. This method helps much, but it can't completely
avoid stop.
Reset the IRDA before every time sending the data is more safe.
Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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framework
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (34 commits)
nfsd race fixes: jfs
nfsd race fixes: reiserfs
nfsd race fixes: ext4
nfsd race fixes: ext3
nfsd race fixes: ext2
nfsd/create race fixes, infrastructure
filesystem notification: create fs/notify to contain all fs notification
fs/block_dev.c: __read_mostly improvement and sb_is_blkdev_sb utilization
kill ->dir_notify()
filp_cachep can be static in fs/file_table.c
fix f_count description in Documentation/filesystems/files.txt
make INIT_FS use the __RW_LOCK_UNLOCKED initialization
take init_fs to saner place
kill vfs_permission
pass a struct path * to may_open
kill walk_init_root
remove incorrect comment in inode_permission
expand some comments (d_path / seq_path)
correct wrong function name of d_put in kernel document and source comment
fix switch_names() breakage in short-to-short case
...
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jfs version of Al Viro's nfsd race patches
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... and the same for reiserfs. The difference here is that we need
insert_inode_locked4() to match iget5_locked().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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ext3 analog of the previous patch
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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* make ext2_new_inode() put the inode into icache in locked state
* do not unlock until the inode is fully set up; otherwise nfsd
might pick it in half-baked state.
* make sure that ext2_new_inode() does *not* lead to two inodes with the
same inumber hashed at the same time; otherwise a bogus fhandle coming
from nfsd might race with inode creation:
nfsd: iget_locked() creates inode
nfsd: try to read from disk, block on that.
ext2_new_inode(): allocate inode with that inumber
ext2_new_inode(): insert it into icache, set it up and dirty
ext2_write_inode(): get the relevant part of inode table in cache,
set the entry for our inode (and start writing to disk)
nfsd: get CPU again, look into inode table, see nice and sane on-disk
inode, set the in-core inode from it
oops - we have two in-core inodes with the same inumber live in icache,
both used for IO. Welcome to fs corruption...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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new helpers - insert_inode_locked() and insert_inode_locked4().
Hash new inode, making sure that there's no such inode in icache
already. If there is and it does not end up unhashed (as would
happen if we have nfsd trying to resolve a bogus fhandle), fail.
Otherwise insert our inode into hash and succeed.
In either case have i_state set to new+locked; cleanup ends up
being simpler with such calling conventions.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Creating a generic filesystem notification interface, fsnotify, which will be
used by inotify, dnotify, and eventually fanotify is really starting to
clutter the fs directory. This patch simply moves inotify and dnotify into
fs/notify/inotify and fs/notify/dnotify respectively to make both current fs/
and future notification tidier.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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- iget5_locked in bdget really needs blockdev_superblock, instead of
bd_mnt, so bd_mnt could be just a local variable;
- blockdev_superblock really needs __read_mostly, while local var bd_mnt
not;
- make use of sb_is_blkdev_sb in bd_forget, instead of direct reference
to blockdev_superblock.
Signed-off-by: Denis ChengRq <crquan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Remove the hopelessly misguided ->dir_notify(). The only instance (cifs)
has been broken by design from the very beginning; the objects it creates
are never destroyed, keep references to struct file they can outlive, nothing
that could possibly evict them exists on close(2) path *and* no locking
whatsoever is done to prevent races with close(), should the previous, er,
deficiencies someday be dealt with.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Instead of creating the "filp" kmem_cache in vfs_caches_init(),
we can do it a litle be later in files_init(), so that filp_cachep
is static to fs/file_table.c
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Documentation/filesystems/files.txt was not updated when
f_count became an atomic_long_t.
atomic_long_inc_not_zero() is now used instead of atomic_inc_not_zero()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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[AV: rediffed on top of unification of init_fs]
Initialization of init_fs still uses the deprecated RW_LOCK_UNLOCKED macro.
This patch updates it to use the __RW_LOCK_UNLOCKED(lock) macro.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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With all the nameidata removal there's no point anymore for this helper.
Of the three callers left two will go away with the next lookup series
anyway.
Also add proper kerneldoc to inode_permission as this is the main
permission check routine now.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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No need for the nameidata in may_open - a struct path is enough.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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walk_init_root is a tiny helper that is marked __always_inline, has just
one caller and an unused argument. Just merge it into the caller.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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We now pass on all MAY_ flags to the filesystems permission routines,
so remove the comment stating the contrary.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Explain that you really need to use the return value of d_path rather than
the buffer you passed into it.
Also fix the comment for seq_path(), the function arguments changed
recently but the comment hadn't been updated in sync.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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no function named d_put(), it should be dput().
Impact: fix document and comment, no functionality changed
Signed-off-by: Zhao Lei <zhaolei@cn.fuijtsu.com>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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We want ->name.len to match the resulting name on *both*
source and target
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Ensure fast symlink targets are NUL-terminated, even if corrupted
on-disk.
Cc: Sergey S. Kostyliov <rathamahata@php4.ru>
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Ensure fast symlink targets are NUL-terminated, even if corrupted
on-disk.
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Ensure fast symlink targets are NUL-terminated, even if corrupted
on-disk.
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Ensure fast symlink targets are NUL-terminated, even if corrupted
on-disk.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: adilger@sun.com
Cc: linux-ext4@vger.kernel.org
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Ensure fast symlink targets are NUL-terminated, even if corrupted
on-disk.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: linux-ext4@vger.kernel.org
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Ensure fast symlink targets are NUL-terminated, even if corrupted
on-disk.
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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On-disk data corruption could cause a page link to have its i_size set
to PAGE_SIZE (or a multiple thereof) and its contents all non-NUL.
NUL-terminate the link name to ensure this doesn't cause further
problems for the kernel.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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A number of filesystems were potentially triggering kernel bugs due to
corrupted symlink names on disk. This function helps safely terminate
the names.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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The result from readlink is being used to index into the link name
buffer without checking whether it is a valid length. If readlink
returns an error this will fault or cause memory corruption.
Cc: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Cc: Dustin Kirkland <kirkland@canonical.com>
Cc: ecryptfs-devel@lists.launchpad.net
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Acked-by: Michael Halcrow <mhalcrow@us.ibm.com>
Acked-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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The extra semicolon serves no purpose.
Signed-off-by: Julia Lawall <julia@diku.dk>
Reviewed-by: Richard Genoud <richard.genoud@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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include/linux/fs.h contains externs for a bunch of variables. That obviously
belongs under ifdef __KERNEL__.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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struct dentry is one of the most critical structures in the kernel. So it's
sad to see it going neglected.
With CONFIG_PROFILING turned on (which is probably the common case at least
for distros and kernel developers), sizeof(struct dcache) == 208 here
(64-bit). This gives 19 objects per slab.
I packed d_mounted into a hole, and took another 4 bytes off the inline
name length to take the padding out from the end of the structure. This
shinks it to 200 bytes. I could have gone the other way and increased the
length to 40, but I'm aiming for a magic number, read on...
I then got rid of the d_cookie pointer. This shrinks it to 192 bytes. Rant:
why was this ever a good idea? The cookie system should increase its hash
size or use a tree or something if lookups are a problem. Also the "fast
dcookie lookups" in oprofile should be moved into the dcookie code -- how
can oprofile possibly care about the dcookie_mutex? It gets dropped after
get_dcookie() returns so it can't be providing any sort of protection.
At 192 bytes, 21 objects fit into a 4K page, saving about 3MB on my system
with ~140 000 entries allocated. 192 is also a multiple of 64, so we get
nice cacheline alignment on 64 and 32 byte line systems -- any given dentry
will now require 3 cachelines to touch all fields wheras previously it
would require 4.
I know the inline name size was chosen quite carefully, however with the
reduction in cacheline footprint, it should actually be just about as fast
to do a name lookup for a 36 character name as it was before the patch (and
faster for other sizes). The memory footprint savings for names which are
<= 32 or > 36 bytes long should more than make up for the memory cost for
33-36 byte names.
Performance is a feature...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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