Remove dead pieces of code under "if (c->min_io_size == 1)" statement -
we never execute it because in UBIFS 'c->min_io_size' is always at least 8.
This are leftovers from old pre-mainline prototype.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Remove unnecessary brackets in "inode->i_flags |= (S_NOCMTIME)" statement to
make the code not look silly.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Instead of using long "(inode->i_mode & S_IFMT) != S_IFREG" expression, use
shorted "!S_ISREG(inode->i_mode)".
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Teach 'dbg_dump_inode()' dump directory entries for directory inodes.
This requires few additional changes:
1. The 'c' argument of 'dbg_dump_inode()' cannot be const any more.
2. Users of 'dbg_dump_inode()' should not have 'tnc_mutex' locked.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch lessens the 'struct ubifs_debug_info' size by 90 bytes by
allocating less bytes for the debugfs root directory name. It introduces macros
for the name patter an length instead of hard-coding 100 bytes. It also makes
UBIFS use 'snprintf()' and teaches it to gracefully catch situations when the
name array is too short.
Additionally, this patch makes 2 unrelated changes - I just thought they do not
deserve separate commits: simplifies 'ubifs_assert()' for non-debugging case
and makes 'dbg_debugfs_init()' properly verify debugfs return code which may be
an error code or NULL, so we should you 'IS_ERR_OR_NULL()' instead of
'IS_ERR()'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
If commit failed and it is in broken state, UBIFS switches to R/O mode. Most
operations return -EROFS in this case, except of commit which returns -EINVAL.
Make it return -EROFS too for consistency. This is also important for our power
cut emulation testing.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
d251ed271d "ubifs: fix sget races" left out the goto from this
error path so the static checkers complain that we're dereferencing
"sb" when it's an ERR_PTR.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* allocate ubifs_info in ->mount(), fill it enough for sb_test() and
set ->s_fs_info to it in set() callback passed to sget().
* do *not* free it in ->put_super(); do that in ->kill_sb() after we'd
done kill_anon_super().
* don't free it in ubifs_fill_super() either - deactivate_locked_super()
done by caller when ubifs_fill_super() returns an error will take care
of that sucker.
* get rid of kludge with passing ubi to ubifs_fill_super() in ->s_fs_info;
we only need it in alloc_ubifs_info(), so ubifs_fill_super() will need
only ubifs_info. Which it will find in ->s_fs_info just fine, no need to
reassign anything...
As the result, sb_test() becomes safe to apply to all superblocks that
can be found by sget() (and a kludge with temporary use of ->s_fs_info
to store a pointer to very different structure goes away).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The free space fixup is currently initiated during mount after the call to
ubifs_write_master() which results in a write to PEBs; this has been observed
with the patch 'assert no fixup when writing a node' applied:
Move the free space fixup on mount to before the calls to
ubifs_recover_inl_heads() and ubifs_write_master(). This results in no
assertions with the previously mentioned patch applied.
Artem: tweaked the patch a bit
Signed-off-by: Ben Gardiner <bengardiner@nanometrics>
Reviewed-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The current 'mount_ubifs()' implementation does not initialize the LPT until the
the master node is marked dirty. Move the LPT initialization to before marking
the master node dirty. This is a preparation for the next patch which will move
the free-space-fixup check to before marking the master node dirty, because we
have to fix-up the free space before doing any writes.
Artem: massaged the patch and commit message.
Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Reviewed-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The current free space fixup can result in some writing to the UBI volume
when the space_fixup flag is set.
To catch instances where UBIFS is writing to the NAND while the space_fixup
flag is set, add an assert to ubifs_write_node().
Artem: tweaked the patch, added similar assertion to the write buffer
write path.
Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Reviewed-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBIFS maintains per-filesystem and global clean znode counters
('c->clean_zn_cnt' and 'ubifs_clean_zn_cnt'). It is important to maintain
correct values there since the shrinker relies on 'ubifs_clean_zn_cnt'.
However, in case of failures during commit the counters were corrupted. E.g.,
if a failure happens in the middle of 'write_index()', then some nodes in the
commit list ('c->cnext') are marked as clean, and some are marked as dirty. And
the 'ubifs_destroy_tnc_subtree()' frees does not retrun correct count, and we
end up with non-zero 'c->clean_zn_cnt' when unmounting. This means that if we
have 2 file-sytem and one of them fails, and we unmount it,
'ubifs_clean_zn_cnt' stays incorrect and confuses the shrinker.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBIFS leaks memory on error path in 'ubifs_jnl_update()' in case of write
failure because it forgets to free the 'struct ubifs_dent_node *dent' object.
Although the object is small, the alignment can make it large - e.g., 2KiB
if the min. I/O unit is 2KiB.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
Sometimes VM asks the shrinker to return amount of objects it can shrink,
and we return the ubifs_clean_zn_cnt in that case. However, it is possible
that this counter is negative for a short period of time, due to the way
UBIFS TNC code updates it. And I can observe the following warnings sometimes:
shrink_slab: ubifs_shrinker+0x0/0x2b7 [ubifs] negative objects to delete nr=-8541616642706119788
This patch makes sure UBIFS never returns negative count of objects.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
Unfortunately, the recovery fix d1606a59b6be4ea392eabd40d1250aa1eeb19efb
(UBIFS: fix extremely rare mount failure) broke recovery. This commit make
UBIFS drop the last min. I/O unit in all journal heads, but this is needed only
for the GC head. And this does not work for non-GC heads. For example, if
suppose we have min. I/O units A and B, and A contains a valid node X, which
was fsynced, and then a group of nodes Y which spans the rest of A and B. In
this case we'll drop not only Y, but also X, which is obviously incorrect.
This patch fixes the issue and additionally makes recovery to drop last min.
I/O unit only for the GC head, and leave things as they have been for ages for
the other heads - this is safer.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Instead of passing "grouped" parameter to 'ubifs_recover_leb()' which tells
whether the nodes are grouped in the LEB to recover, pass the journal head
number and let 'ubifs_recover_leb()' look at the journal head's 'grouped' flag.
This patch is a preparation to a further fix where we'll need to know the
journal head number for other purposes.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Journal heads are different in a way how UBIFS writes nodes there. All normal
journal heads receive grouped nodes, while the GC journal heads receives
ungrouped nodes. This patch adds a 'grouped' flag to 'struct ubifs_jhead' which
describes this property.
This patch is a preparation to a further recovery fix.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Commit ab51afe05273741f72383529ef488aa1ea598ec6 was a good clean-up, but
it introduced a regression - now UBIFS prints scary error messages during
recovery on all corrupted nodes, even though the corruptions are expected
(due to a power cut). This patch fixes the issue.
Additionally fix a typo in a commentary introduced by the same commit.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Commit 1495f230fa ("vmscan: change shrinker API by passing
shrink_control struct") changed the API of ->shrink(), but missed ubifs
and cifs instances.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ubifs does not have problems with references to unlinked directories.
CC: Artem Bityutskiy <dedekind1@gmail.com>
CC: Adrian Hunter <adrian.hunter@nokia.com>
CC: linux-mtd@lists.infradead.org
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Tell the filesystem if we just updated timestamp (I_DIRTY_SYNC) or
anything else, so that the filesystem can track internally if it
needs to push out a transaction for fdatasync or not.
This is just the prototype change with no user for it yet. I plan
to push large XFS changes for the next merge window, and getting
this trivial infrastructure in this window would help a lot to avoid
tree interdependencies.
Also remove incorrect comments that ->dirty_inode can't block. That
has been changed a long time ago, and many implementations rely on it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (25 commits)
cifs: remove unnecessary dentry_unhash on rmdir/rename_dir
ocfs2: remove unnecessary dentry_unhash on rmdir/rename_dir
exofs: remove unnecessary dentry_unhash on rmdir/rename_dir
nfs: remove unnecessary dentry_unhash on rmdir/rename_dir
ext2: remove unnecessary dentry_unhash on rmdir/rename_dir
ext3: remove unnecessary dentry_unhash on rmdir/rename_dir
ext4: remove unnecessary dentry_unhash on rmdir/rename_dir
btrfs: remove unnecessary dentry_unhash in rmdir/rename_dir
ceph: remove unnecessary dentry_unhash calls
vfs: clean up vfs_rename_other
vfs: clean up vfs_rename_dir
vfs: clean up vfs_rmdir
vfs: fix vfs_rename_dir for FS_RENAME_DOES_D_MOVE filesystems
libfs: drop unneeded dentry_unhash
vfs: update dentry_unhash() comment
vfs: push dentry_unhash on rename_dir into file systems
vfs: push dentry_unhash on rmdir into file systems
vfs: remove dget() from dentry_unhash()
vfs: dentry_unhash immediately prior to rmdir
vfs: Block mmapped writes while the fs is frozen
...
Only a few file systems need this. Start by pushing it down into each
rename method (except gfs2 and xfs) so that it can be dealt with on a
per-fs basis.
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Only a few file systems need this. Start by pushing it down into each
fs rmdir method (except gfs2 and xfs) so it can be dealt with on a per-fs
basis.
This does not change behavior for any in-tree file systems.
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Switch to debugging using dynamic printk (pr_debug()). There is no good reason
to carry custom debugging prints if there is so cool and powerful generic
dynamic printk infrastructure, see Documentation/dynamic-debug-howto.txt. With
dynamic printks we can switch on/of individual prints, per-file, per-function
and per format messages. This means that instead of doing old-fashioned
echo 1 > /sys/module/ubifs/parameters/debug_msgs
to enable general messages, we can do:
echo 'format "UBIFS DBG gen" +ptlf' > control
to enable general messages and additionally ask the dynamic printk
infrastructure to print process ID, line number and function name. So there is
no reason to keep UBIFS-specific crud if there is more powerful generic thing.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This is a minor fix for UBIFS kernel-doc comments - we forgot the "@" symbol
for several 'struct ubifs_debug_info'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch fixes an extremely rare mount failure after a power cut, when mount
fails with ENOSPC error because UBIFS could not find the GC LEB.
In short, the reason for this failure is that after recovery the GC head LEB
contains less free space than it had contained just before the power cut
happened. As a result, if the FS is full, 'ubifs_rcvry_gc_commit()' is unable
to find a dirty LEB to GC and a free LEB, so mount fails.
This patch contains a huge comment with more detailed explanation, please refer
that comment.
Since this is really really rare and unlikely situation, I do not send this
patch to the stable tree, also because it requires a lot of preparation
patches which I did before. So sending this to -stable would be too risky.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Further simplify 'ubifs_recover_leb()' by noticing that we have to call
'clean_buf()' in any case, and it is fine to call it if the offset is
aligned to 'c->min_io_size'. Thus, we do not have to call it separately
from every "if" - just call it once at the end.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Now when we call 'ubifs_recover_leb()' only for LEBs which are potentially
corrupted (i.e., only for last buds, not for all of them), we can cleanup every
LEB, not only those where we find corruption. The reason - unstable bits. Even
though the LEB may look good now, it might contain unstable bits which may hit
us a bit later.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch cleans up 'ubifs_recover_leb()' function and makes it more readable.
Move things which are done only once out of the loop and kill unneeded 'switch'
statement.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
If a UBIFS filesystem is being mounted read-write, or is being remounted
from read-only to read-write, check for the "space_fixup" flag and fix
all LEBs containing empty space if necessary.
Artem: tweaked the patch a bit
Signed-off-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch adds the 'ubifs_fixup_free_space()' function which scans all
LEBs in the filesystem for those that are in-use but have one or more
empty pages, then re-maps the LEBs in order to erase the empty portions.
Afterward it removes the "space_fixup" flag from the UBIFS superblock.
Artem: massaged the patch
Signed-off-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The 'space_fixup' flag can be set in the superblock of a new filesystem by
mkfs.ubifs to indicate that any eraseblocks with free space remaining should be
fixed-up the first time it's mounted (after which the flag is un-set). This
means that the UBIFS image has been flashed by a "dumb" flasher and the free
space has been actually programmed (writing all 0xFFs), so this free space
cannot be used. UBIFS fixes the free space up by re-writing the contents of all
LEBs with free space using the atomic LEB change UBI operation.
Artem: improved commit message, add some more commentaries to the code.
Signed-off-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
We'll need to use the 'next_log_lnum()' helper function from log.c in the fixup
code, so let's move it to misc.h. IOW, this is a preparation to the following
free space fixup changes.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch improves UBIFS recovery and teaches it to expect corruption only
in the last buds. Indeed, currently we just recover all buds, which is
incorrect because only the last buds can have corruptions in case of a power
cut. So it is inconsistent with the rest of the recovery strategy which tries
hard to distinguish between corruptions cause by power cuts and other types of
corruptions.
This patch also adds one quirk - a bit older UBIFS was could have corruption in
the next to last bud because of the way it switched buds: when bud A is full,
it first searched for the next bud B, the wrote a reference node to the log
about B, and then synchronized the write-buffer of A. So we could end up with
buds A and B, where B is the last, but A had corruption. The UBIFS behavior
was fixed, though, so currently it always first synchronizes A's write-buffer
and only after this adds B to the log. However, to be make sure that we handle
unclean (after a power cut) UBIFS images belonging to older UBIFS - we need to
add a quirk and keep it for some time: we need to check for the situation
described above.
Thankfully, it is easy to check for that situation. When UBIFS adds B to the
log, it always first unmaps B, then maps it, and then syncs A's write-buffer.
Thus, in that situation we can check that B is empty, in which case it is OK to
have corruption in A. To check that B is empty it is enough to just read the
first few bytes of the bud and compare them with 0xFFs. This quirk may be
removed in a couple of years.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Currently when UBIFS fills up the current bud (which is the last in the journal
head) and switches to the next bud, it first writes the log reference node for
the next bud and only after this synchronizes the write-buffer of the previous
bud. This is not a big deal, but an unclean power cut may lead to a situation
when we have corruption in a next-to-last bud, although it is much more logical
that we have to have corruption only in the last bud.
This patch also removes write-buffer synchronization from
'ubifs_wbuf_seek_nolock()' because this is not needed anymore (we synchronize
the write-buffer explicitly everywhere now) and also because this is just
prone to various errors.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Remove a 'BUG()' statement when we are unable to find a bud and add a
similar 'ubifs_assert()' statement instead.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This is a minor preparation patch which changes 'replay_bud()' interface -
instead of passing bud lnum, offs, jhead, etc directly, pass a pointer to the
bud entry which contains all the information. The bud entry will be also needed
in one of the following patches.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch simplifies replay even further - it removes the replay tree and
adds the replay list instead. Indeed, we just do not need to use a tree here -
all we need to do is to add all nodes to the list and then sort it. Using
RB-tree is an overkill - more code and slower. And since we replay buds in
order, we expect the nodes to follow in _mostly_ sorted order, so the merge
sort becomes much cheaper in average than an RB-tree.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch simplifies the replay code and makes it smaller. First of all, we
can notice that we do not really need to create bud replay entries and insert
them to the replay tree, because the only reason we do this is to set buds
lprops correctly at the end. Instead, we can just walk the list of buds at the
very end and set lprops for each bud. This allows us to get rid of whole
'insert_ref_node()' function, the 'REPLAY_REF' flag, and several fields in
'struct replay_entry'. Then we can also notice that we do not need the 'flags'
'struct replay_entry' field, because there is only one flag -
'REPLAY_DELETION'. Instead, we can just add a 'deletion' bit fields. As a
result, this patch deletes much more lines that in adds.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This is just a small preparation patch which adds 'free' and 'drity' fields to
'struct bud_entry'. They will be used to set bud lprops.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This is patch removes an unnecessary 'offs' variable from 'ubifs_wbuf_write_nolock()'
- we can just keep 'wbuf->offs' up-to-date instead. This patch is very minor
the only motivation for it was that it is cleaner to keep wbuf->offs up-to-date
by the time we call 'ubifs_leb_write()'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Commit 52c6e6f990 provides misleading infomation
in the commit messages - buds are replied in order. And the real reason why
that fix helped is probably because it made sure we seek head even in read-only
mode (so deferred recovery will have seeked heads).
This patch adds an assertion which will fire if we reply buds out of order.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This is a minor change which makes 2 functions static because they
are not used outside the gc.c file: 'data_nodes_cmp()' and
'nondata_nodes_cmp()'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Now we return all errors from 'scan_check_cb()' directly, so we do not need
'struct scan_check_data' any more, and this patch removes it.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Simplify error path in 'scan_check_cb()' and stop using the special 'data->err'
field, but instead return the error code directly.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
When doing the lprops extra check ('dbg_check_lprops()') we scan whole media.
We even scan empty and freeable LEBs which may contain garbage, which we handle
after scanning. This patch teach the lprops checking function
('scan_check_cb()') to avoid scanning for free and freeable LEBs and save time.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
When re-mounting from R/O mode to R/W mode and the LEB count in the superblock
is not up-to date, because for the underlying UBI volume became larger, we
re-write the superblock. We allocate RAM for these purposes, but never free it.
So this is a memory leak, although very rare one.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
This patch fixes a problem with the following symptoms:
UBIFS: deferred recovery completed
UBIFS error (pid 15676): dbg_check_synced_i_size: ui_size is 11481088, synced_i_size is 11459081, but inode is clean
UBIFS error (pid 15676): dbg_check_synced_i_size: i_ino 128, i_mode 0x81a4, i_size 11481088
It happens when additional debugging checks are enabled and we are recovering
from a power cut. When we fixup corrupted inode size during recovery, we change
them in-place and we change ui_size as well, but not synced_i_size, which
causes this failure. This patch makes sure we change both fields and fixes the
issue.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
When the debugging self-checks are enabled, we go trough whole file-system
after mount and check/validate every single node referred to by the index.
This is implemented by the 'dbg_check_filesystem()' function. However, this
function fails if we mount "unclean" file-system, i.e., if we mount the
file-system after a power cut. It fails with the following symptoms:
UBIFS DBG (pid 8171): ubifs_recover_size: ino 937 size 3309925 -> 3317760
UBIFS: recovery deferred
UBIFS error (pid 8171): check_leaf: data node at LEB 1000:0 is not within inode size 3309925
The reason of failure is that recovery fixed up the inode size in memory, but
not on the flash so far. So the value on the flash is incorrect so far,
and would be corrected when we re-mount R/W. But 'check_leaf()' ignores
this fact and tries to validate the size of the on-flash inode, which is
incorrect, so it fails.
This patch teaches the checking code to look at the VFS inode cache first,
and if there is the inode in question, use that inode instead of the inode
on the flash media. This fixes the issue.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
In 'ubifs_recover_size()' we have an "if (!e->inode && c->ro_mount)" statement.
But if 'c->ro_mount' is true, then '!e->inode' must always be true as well. So
we can remove the unnecessary '!e->inode' test and put an
'ubifs_assert(!e->inode)' instead.
This patch also removes an extra trailing white-space in a debugging print,
as well as adds few empty lines to 'ubifs_recover_size()' to make it a bit more
readable.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
When recovering the inode size, one of the debugging messages was printed
incorrecly, this patches fixes it.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This commits refactors and cleans up 'ubifs_rcvry_gc_commit()' which was quite
untidy, also removes the commentary which was not 100% correct.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Split the 'ubifs_rcvry_gc_commit()' function and introduce a 'grab_empty_leb()'
heler. This cleans 'ubifs_rcvry_gc_commit()' a little and makes it a bit less
of spagetti.
Also, add a commentary which explains why it is crucial to first search for an
empty LEB and then run commit.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
When UBIFS is in the failure mode (used for power cut emulation testing) we for
some reasons do not dump the stack in many places, e.g., in assertions.
Probably at early days we had too many of them and disabled this to make the
development easier, but then never enabled. Nowadays I sometimes observe
assertion failures during power cut testing, but the useful stackdump is not
printed, which is bad. This patch makes UBIFS always print the stackdump when
debugging is enabled.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
If we fail to recover the gc_lnum we just return an error and it then
it is difficult to figure out why this happened. This patch adds useful
debugging information which should make it easier to debug the failure.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch removes a piece of code in 'ubifs_rcvry_gc_commit()' which is never
executed. We call 'ubifs_find_dirty_leb()' function with min_space =
wbuf->offs, so if it returns us an LEB, it is guaranteed to have at lease
'wbuf->offs' bytes of free+dirty space. So we can remove the subsequent code
which deals with "returned LEB has less than 'wbuf->offs' bytes of free+dirty
space". This simplifies 'ubifs_rcvry_gc_commit()' a little.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
We have duplicated code in 'ubifs_garbage_collect()' and
'ubifs_rcvry_gc_commit()', which is about handling the special case of free
LEB. In both cases we just want to garbage-collect the LEB using
'ubifs_garbage_collect_leb()'.
This patch teaches 'ubifs_garbage_collect_leb()' to handle free LEB's so that
the caller does not have to do this and the duplicated code is removed.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Remove the following commentary from 'ubifs_file_mmap()':
/* 'generic_file_mmap()' takes care of NOMMU case */
I do not understand what it means, and I could not find anything relater to
NOMMU in 'generic_file_mmap()'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch is a tiny improvement which removes few bytes of code.
UBIFS debugfs files are non-seekable and the file position is ignored,
so do not increase it in the write handler.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The 'dbg_dump_lprop()' is trying to detect journal head LEBs when printing,
so it looks at the write-buffers. However, if we are in R/O mode, we
de-allocate the write-buffers, so 'dbg_dump_lprop()' oopses. This patch fixes
the issue.
Note, this patch is not critical, it is only about the debugging code path, and
it is unlikely that anyone but UBIFS developers would ever hit this issue.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
We have our own flags indicating R/O mode, and c->ro_mode is equivalent
to MS_RDONLY. Let's be consistent and use UBIFS flags everywhere.
This patch is just a minor cleanup.
Additionally, add a comment that we are surprised with VFS behavior -
as a reminder to look at this some day.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
When the debugging failure emulation is enabled and UBIFS decides to
emulate an I/O error, it uses EIO error code. In which case UBIFS
switches into R/O mode later on. The for the user-space is that when
a failure is emulated, the file-system sometimes returns EIO and
sometimes EROFS. This makes it more difficult to implement user-space
tests for the failure mode. Let's be consistent and return EROFS in
all the cases.
This patch is an improvement for the debugging code and does not affect
the functionality at all.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This is just a tiny clean-up patch. The variable name for empty address
space operations is "empty_aops". Let's use consistent names for empty
inode and file operations: "empty_iops" and "empty_fops", instead of
inconsistent "none_inode_operations" and "none_file_operations".
Artem: re-write the commit message.
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Try to improve UBIFS testing coverage by randomly picking LEBs to
store in lsave, rather than picking them optimally. Create a debugging
version of 'populate_lsave()' for these purposes and enable it when
general debugging self-checks are enabled.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBIFS can force itself to use the 'in-the-gaps' commit method - the last resort
method which is normally invoced very very rarely. Currently this "force
int-the-gaps" debugging feature is a separate test mode. But it is a bit saner
to make it to be the "general" self-test check instead.
This patch is just a clean-up which should make the debugging code look a bit
nicer and easier to use - we have way too many debugging options.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch improves the 'dbg_check_space_info()' function which checks
whether the amount of space before re-mounting and after re-mounting
is the same (remounting from R/O to R/W modes and vice-versa).
The problem is that 'dbg_check_space_info()' does not save the budgeting
information before re-mounting, so when an error is reported, we do not
know why the amount of free space changed.
This patches makes the following changes:
1. Teaches 'dbg_dump_budg()' function to accept a 'struct ubifs_budg_info'
argument and print out the this argument. This way we may ask it to
print any saved budgeting info, no only the current one.
2. Accordingly changes all the callers of 'dbg_dump_budg()' to comply with
the changed interface.
3. Introduce a 'saved_bi' (saved budgeting info) field to
'struct ubifs_debug_info' and save the budgeting info before re-mounting
there.
4. Change 'dbg_check_space_info()' and make it print both old and new
budgeting information.
5. Additionally, save 'c->igx_gc_cnt' and print it if and error happens. This
value contributes to the amount of free space, so we have to print it.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Re-arrange the budget dump and make sure we first dump all
the 'struct ubifs_budg_info' fields, and then the other information.
Additionally, print the 'uncommitted_idx' variable.
This change is required for to the following dumping function
enhancement where it will be possible to dump saved
'struct ubifs_budg_info' objects, not only the current one.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
The current 'dbg_dump_budg()' calling convention is that the
'c->space_lock' spinlock is held. However, none of the callers
actually use it from contects which have 'c->space_lock' locked,
so all callers have to explicitely lock and unlock the spinlock.
This is not very sensible convention. This patch changes it and
makes 'dbg_dump_budg()' lock the spinlock instead of imposing this
to the callers. This simplifies the code a little.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch separates out all the budgeting-related information
from 'struct ubifs_info' to 'struct ubifs_budg_info'. This way the
code looks a bit cleaner. However, the main driver for this is
that we want to save budgeting information and print it later,
so a separate data structure for this is helpful.
This patch is a preparation for the further debugging output
improvements.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
There was an attempt to standartize various "__attribute__" and
other macros in order to have potentially portable and more
consistent code, see commit 82ddcb0405.
Note, that commit refers Rober Love's blog post, but the URL
is broken, the valid URL is:
http://blog.rlove.org/2005/10/with-little-help-from-your-compiler.html
Moreover, nowadays checkpatch.pl warns about using
__attribute__((packed)):
"WARNING: __packed is preferred over __attribute__((packed))"
It is not a big deal for UBIFS to use __packed, so let's do it.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Fix several minor stylistic issues:
* lines longer than 80 characters
* space before closing parenthesis ')'
* spaces in the indentations
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Turn the debufs files UBIFS maintains into non-seekable. Indeed, none
of them is supposed to be seek'ed.
Do this by making the '.lseek()' handler to be 'no_llseek()' and by
using 'nonseekable_open()' in the '.open()' operation.
This does mean an API break but this debugging API is only used by a couple
of test scripts which do not rely in the 'llseek()' operation.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This is the second fix of the following symptom:
UBIFS error (pid 34456): could not find an empty LEB
which sometimes happens after power cuts when we mount the file-system - UBIFS
refuses it with the above error message which comes from the
'ubifs_rcvry_gc_commit()' function. I can reproduce this using the integck test
with the UBIFS power cut emulation enabled.
Analysis of the problem.
Currently UBIFS replay seeks the journal heads to the last _replayed_ bud.
But the buds are replayed out-of-order, so the replay basically seeks journal
heads to the "random" bud belonging to this head, and not to the _last_ one.
The result of this is that the GC head may be seeked to a full LEB with no free
space, or very little free space. And 'ubifs_rcvry_gc_commit()' tries to find a
fully or mostly dirty LEB to match the current GC head (because we need to
garbage-collect that dirty LEB at one go, because we do not have @c->gc_lnum).
So 'ubifs_find_dirty_leb()' fails and we fall back to finding an empty LEB and
also fail. As a result - recovery fails and mounting fails.
This patch teaches the replay to initialize the GC heads exactly to the latest
buds, i.e. the buds which have the largest sequence number in corresponding
log reference nodes.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
Currently UBIFS has a small optimization - it frees write-buffers when it is
re-mounted from R/W mode to R/O mode. Of course, when it is mounted R/O, it
does not allocate write-buffers as well.
This optimization is nice but it leads to subtle problems and complications
in recovery, which I can reproduce using the integck test. The symptoms are
that after a power cut the file-system cannot be mounted if we first mount
it R/O, and then re-mount R/W - 'ubifs_rcvry_gc_commit()' prints:
UBIFS error (pid 34456): could not find an empty LEB
Analysis of the problem.
When mounting R/W, the reply process sets journal heads to buds [1], but
when mounting R/O - it does not do this, because the write-buffers are not
allocated. So 'ubifs_rcvry_gc_commit()' works completely differently for the
same file-system but for the following 2 cases:
1. mounting R/W after a power cut and recover
2. mounting R/O after a power cut, re-mounting R/W and run deferred recovery
In the former case, we have journal heads seeked to the a bud, in the latter
case, they are non-seeked (wbuf->lnum == -1). So in the latter case we do not
try to recover the GC LEB by garbage-collecting to the GC head, but we just
try to find an empty LEB, and there may be no empty LEBs, so we just fail.
On the other hand, in the former case (mount R/W), we are able to make a GC LEB
(@c->gc_lnum) by garbage-collecting.
Thus, let's remove this small nice optimization and always allocate
write-buffers. This should not make too big difference - we have only 3
of them, each of max. write unit size, which is usually 2KiB. So this is
about 6KiB of RAM for the typical case, and only when mounted R/O.
[1]: Note, currently the replay process is setting (seeking) the journal heads
to _some_ buds, not necessarily to the buds which had been the journal heads
before the power cut happened. This will be fixed separately.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
This patch fixes the following symptoms:
1. Unmount UBIFS cleanly.
2. Start mounting UBIFS R/W and have a power cut immediately
3. Start mounting UBIFS R/O, this succeeds
4. Try to re-mount UBIFS R/W - this fails immediately or later on,
because UBIFS will write the master node to the flash area
which has been written before.
The analysis of the problem:
1. UBIFS is unmounted cleanly, both copies of the master node are clean.
2. UBIFS is being mounter R/W, starts changing master node copy 1, and
a power cut happens. The copy N1 becomes corrupted.
3. UBIFS is being mounted R/O. It notices the copy N1 is corrupted and
reads copy N2. Copy N2 is clean.
4. Because of R/O mode, UBIFS cannot recover copy 1.
5. The mount code (ubifs_mount()) sees that the master node is clean,
so it decides that no recovery is needed.
6. We are re-mounting R/W. UBIFS believes no recovery is needed and
starts updating the master node, but copy N1 is still corrupted
and was not recovered!
Fix this problem by marking the master node as dirty every time we
recover it and we are in R/O mode. This forces further recovery and
the UBIFS cleans-up the corruptions and recovers the copy N1 when
re-mounting R/W later.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
When UBIFS switches to R/O mode because it detects I/O failures, then
when we unmount, we still may have allocated budget, and the assertions
which verify that we have not budget will fire. But it is expected to
have the budget in case of I/O failures, so the assertion warnings will
be false. Suppress them for the I/O failure case.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch fixes UBIFS mount failure when the debugging support is enabled,
we are recovering from a power cut, we were first mounter R/O and we are
re-mounting R/W. In this case we should not assume that the amount of free
space before we have re-mounted R/W and after are equivalent, because
when we have mounted R/O the file-system is in a non-committed state so
the amount of free space is slightly smaller, due to the fact that we cannot
predict the amount of free space precisely before we commit.
This patch fixes the issue by skipping the debugging check in case of
recovery. This issue was reported by Caizhiyong <caizhiyong@huawei.com>
here: http://thread.gmane.org/gmane.linux.drivers.mtd/34350/focus=34387
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reported-by: Caizhiyong <caizhiyong@huawei.com>
Cc: stable@kernel.org [2.6.30+]
When compiling UBIFS with CONFIG_UBIFS_FS_DEBUG not set,
gcc-4.5.2 generates a slew of "warning: statement with no effect"
on references to non-void functions defined as 0.
To avoid these warnings, replace #defines with dummy inline functions.
Artem: massage the patch a bit, also remove the duplicate
'dbg_check_lprops()' prototype.
Signed-off-by: Maksim Rayskiy <maksim.rayskiy@gmail.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch fixes severe UBIFS bug: UBIFS oopses when we 'fsync()' an
file on R/O-mounter file-system. We (the UBIFS authors) incorrectly
thought that VFS would not propagate 'fsync()' down to the file-system
if it is read-only, but this is not the case.
It is easy to exploit this bug using the following simple perl script:
use strict;
use File::Sync qw(fsync sync);
die "File path is not specified" if not defined $ARGV[0];
my $path = $ARGV[0];
open FILE, "<", "$path" or die "Cannot open $path: $!";
fsync(\*FILE) or die "cannot fsync $path: $!";
close FILE or die "Cannot close $path: $!";
Thanks to Reuben Dowle <Reuben.Dowle@navico.com> for reporting about this
issue.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reported-by: Reuben Dowle <Reuben.Dowle@navico.com>
Cc: stable@kernel.org
* 'for-linus' of git://git.infradead.org/ubifs-2.6:
UBI: do not select KALLSYMS_ALL
UBI: do not compare array with NULL
UBI: check if we are in RO mode in the erase routine
UBIFS: fix debugging failure in dbg_check_space_info
UBIFS: fix error path in dbg_debugfs_init_fs
UBIFS: unify error path dbg_debugfs_init_fs
UBIFS: do not select KALLSYMS_ALL
UBIFS: fix assertion warnings
UBIFS: fix oops on error path in read_pnode
UBIFS: do not read flash unnecessarily
With the ->sync_page() hook gone, we have a few users that
add their own static address_space_operations without any
functions defined.
fs/inode.c already has an empty_aops that it uses for init
purposes. Lets export that and use it in the places where
an otherwise empty aops was defined.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This patch fixes a debugging failure with which looks like this:
UBIFS error (pid 32313): dbg_check_space_info: free space changed from 6019344 to 6022654
The reason for this failure is described in the comment this patch adds
to the code. But in short - 'c->freeable_cnt' may be different before
and after re-mounting, and this is normal. So the debugging code should
make sure that free space calculations do not depend on 'c->freeable_cnt'.
A similar issue has been reported here:
http://lists.infradead.org/pipermail/linux-mtd/2011-April/034647.html
This patch should fix it.
For the -stable guys: this patch is only relevant for kernels 2.6.30
onwards.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org [2.6.30+]
The debug interface is substandard and on error returns either
NULL or an error code packed in the pointer. So using "IS_ERR"
for the pointers returned by debugfs function is incorrect.
Instead, we should use IS_ERR_OR_NULL.
This path is an improved vestion of the original patch from
Phil Carmody.
Reported-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
This is just a small clean-up patch which simlifies and unifies the
error path in the dbg_debugfs_init_fs(). We have common error path
for all failure cases in this function except of the very first
case. And this patch makes the first failure case use the same
error path as the other cases by using the 'fname' and 'dent'
variables.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
All UBIFS needs is to make sure we stacktraces when UBIFS debugging
is enabled. It is enough to select KALLSYMS for this, KALLSYMS_ALL
is not necessary. Moreover, Randy Dunlap reported that UBIFS causes
the following Kconfig dependency warning:
warning: (UBIFS_FS_DEBUG && LOCKDEP && LATENCYTOP) selects KALLSYMS_ALL
which has unmet direct dependencies (DEBUG_KERNEL && KALLSYMS)
The reason is that KALLSYMS_ALL requires DEBUG_KERNEL and KALLSYMS, so
ideally, to select KALLSYMS_ALL we'd need to select DEBUG_KERNEL and
KALLSYMS first.
This seems to be too much to select. The easiest way to go is to forget
about KALLSYMS_ALL and just select KALLSYMS when UBIFS debugging is
enabled - that should be enough for stackdumps.
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
This patch fixes UBIFS assertion warnings like:
UBIFS assert failed in ubifs_leb_unmap at 135 (pid 29365)
Pid: 29365, comm: integck Tainted: G I 2.6.37-ubi-2.6+ #34
Call Trace:
[<ffffffffa047c663>] ubifs_lpt_init+0x95e/0x9ee [ubifs]
[<ffffffffa04623a7>] ubifs_remount_fs+0x2c7/0x762 [ubifs]
[<ffffffff810f066e>] do_remount_sb+0xb6/0x101
[<ffffffff81106ff4>] ? do_mount+0x191/0x78e
[<ffffffff811070bb>] do_mount+0x258/0x78e
[<ffffffff810da1e8>] ? alloc_pages_current+0xa2/0xc5
[<ffffffff81107674>] sys_mount+0x83/0xbd
[<ffffffff81009a12>] system_call_fastpath+0x16/0x1b
They happen when we re-mount from R/O mode to R/W mode. While
re-mounting, we write to the media, but we still have the c->ro_mount
flag set. The fix is very simple - just clear the flag before
starting re-mounting R/W.
These warnings are caused by the following commit:
2ef13294d2
For -stable guys: this bug was introduced in 2.6.38, this is materieal
for 2.6.38-stable.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org [2.6.38]
Thanks to coverity which spotted that UBIFS will oops if 'kmalloc()'
in 'read_pnode()' fails and we dereference a NULL 'pnode' pointer
when we 'goto out'.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
This fix makes the 'dbg_check_old_index()' function return
immediately if debugging is disabled, instead of executing
incorrect 'goto out' which causes UBIFS to:
1. Allocate memory
2. Read the flash
On every commit. OK, we do not commit that often, but it is
still silly to do unneeded I/O anyway.
Credits to coverity for spotting this silly issue.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: stable@kernel.org
* 'for-2.6.39/core' of git://git.kernel.dk/linux-2.6-block: (65 commits)
Documentation/iostats.txt: bit-size reference etc.
cfq-iosched: removing unnecessary think time checking
cfq-iosched: Don't clear queue stats when preempt.
blk-throttle: Reset group slice when limits are changed
blk-cgroup: Only give unaccounted_time under debug
cfq-iosched: Don't set active queue in preempt
block: fix non-atomic access to genhd inflight structures
block: attempt to merge with existing requests on plug flush
block: NULL dereference on error path in __blkdev_get()
cfq-iosched: Don't update group weights when on service tree
fs: assign sb->s_bdi to default_backing_dev_info if the bdi is going away
block: Require subsystems to explicitly allocate bio_set integrity mempool
jbd2: finish conversion from WRITE_SYNC_PLUG to WRITE_SYNC and explicit plugging
jbd: finish conversion from WRITE_SYNC_PLUG to WRITE_SYNC and explicit plugging
fs: make fsync_buffers_list() plug
mm: make generic_writepages() use plugging
blk-cgroup: Add unaccounted time to timeslice_used.
block: fixup plugging stubs for !CONFIG_BLOCK
block: remove obsolete comments for blkdev_issue_zeroout.
blktrace: Use rq->cmd_flags directly in blk_add_trace_rq.
...
Fix up conflicts in fs/{aio.c,super.c}
This patch fixes the following UBIFS assertion warning:
UBIFS assert failed in do_readpage at 115 (pid 199)
[<b00321b8>] (unwind_backtrace+0x0/0xdc) from [<af025118>]
(do_readpage+0x108/0x594 [ubifs])
[<af025118>] (do_readpage+0x108/0x594 [ubifs]) from [<af025764>]
(ubifs_write_end+0x1c0/0x2e8 [ubifs])
[<af025764>] (ubifs_write_end+0x1c0/0x2e8 [ubifs]) from
[<b00a0164>] (generic_file_buffered_write+0x18c/0x270)
[<b00a0164>] (generic_file_buffered_write+0x18c/0x270) from
[<b00a08d4>] (__generic_file_aio_write+0x478/0x4c0)
[<b00a08d4>] (__generic_file_aio_write+0x478/0x4c0) from
[<b00a0984>] (generic_file_aio_write+0x68/0xc8)
[<b00a0984>] (generic_file_aio_write+0x68/0xc8) from
[<af024a78>] (ubifs_aio_write+0x178/0x1d8 [ubifs])
[<af024a78>] (ubifs_aio_write+0x178/0x1d8 [ubifs]) from
[<b00d104c>] (do_sync_write+0xb0/0x100)
[<b00d104c>] (do_sync_write+0xb0/0x100) from [<b00d1abc>]
(vfs_write+0xac/0x154)
[<b00d1abc>] (vfs_write+0xac/0x154) from [<b00d1c10>]
(sys_write+0x3c/0x68)
[<b00d1c10>] (sys_write+0x3c/0x68) from [<b002d9a0>]
(ret_fast_syscall+0x0/0x2c)
The 'PG_checked' flag is used to indicate that the page does not
supposedly exist on the media (e.g., a hole or a page beyond the
inode size), so it requires slightly bigger budget, because we have
to account the indexing size increase. And this flag basically
tells that the budget for this page has to be "new page budget".
The "new page budget" is slightly bigger than the "existing page
budget".
The 'do_readpage()' function has the following assertion which
sometimes is hit: 'ubifs_assert(!PageChecked(page))'. Obviously,
the meaning of this assertion is: "I should not be asked to read
a page which does not exist on the media".
However, in 'ubifs_write_begin()' we have a small "trick". Notice,
that VFS may write pages which were not read yet, so the page data
were not loaded from the media to the page cache yet. If VFS tells
that it is going to change only some part of the page, we obviously
have to load it from the media. However, if VFS tells that it is
going to change whole page, we do not read it from the media for
optimization purposes.
However, since we do not read it, we do not know if it exists on
the media or not (a hole, etc). So we set the 'PG_checked' flag
to this page to force bigger budget, just in case.
So 'ubifs_write_begin()' sets 'PG_checked'. Then we are in
'ubifs_write_end()'. And VFS tells us: "hey, for some reasons I
changed my mind and did not change whole page". Frankly, I do not
know why this happens, but I hit this somehow on an ARM platform.
And this is extremely rare.
So in this case UBIFS does the following:
1. Cancels allocated budget.
2. Loads the page from the media by calling 'do_readpage()'.
3. Asks VFS to repeat the whole write operation from the very
beginning (call '->write_begin() again, etc).
And the assertion warning is hit at the step 2 - remember we have
the 'PG_checked' set for this page, and 'do_readpage()' does not
like this. So this patch fixes the problem by adding step 1.5 and
cleaning the 'PG_checked' before calling 'do_readpage()'.
All in all, this patch does not fix any functionality issue, but it
silences UBIFS false positive warning which may happen in very very
rare cases.
And while on it, this patch also improves a commentary which explains
the reasons of setting the 'PG_checked' flag for the page. The old
commentary was a bit difficult to understand.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
