If writeback happens while fuse is in FUSE_NOWRITE condition, the request
will be queued but not processed immediately (see fuse_flush_writepages()).
Until FUSE_NOWRITE becomes relaxed, more writebacks can happen. They will
be queued as "secondary" requests to that first ("primary") request.
Existing implementation crops only primary request. This is not correct
because a subsequent extending write(2) may increase i_size and then
secondary requests won't be cropped properly. The result would be stale
data written to the server to a file offset where zeros must be.
Similar problem may happen if secondary requests are attached to an
in-flight request that was already cropped.
The patch solves the issue by cropping all secondary requests in
fuse_writepage_end(). Thanks to Miklos for idea.
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
fuse_writepage_in_flight() returns false if it fails to find request with
given index in fi->writepages. Then the caller proceeds with populating
data->orig_pages[] and incrementing req->num_pages. Hence,
fuse_writepage_in_flight() must revert changes it made in request before
returning false.
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This allows udev (or more recently systemd-tmpfiles) to create /dev/cuse on
boot, in the same way as /dev/fuse is currently created, and the corresponding
module to be loaded on first access.
The corresponding functionalty was introduced for fuse in commit 578454f.
Signed-off-by: Tom Gundersen <teg@jklm.no>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
If ->writepage() tries to write back a page whose copy is still in flight,
then just skip by calling redirty_page_for_writepage().
This is OK, since now ->writepage() should never be called for data
integrity sync.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
As Maxim Patlasov pointed out, it's possible to get a dirty page while it's
copy is still under writeback, despite fuse_page_mkwrite() doing its thing
(direct IO).
This could result in two concurrent write request for the same offset, with
data corruption if they get mixed up.
To prevent this, fuse needs to check and delay such writes. This
implementation does this by:
1. check if page is still under writeout, if so create a new, single page
secondary request for it
2. chain this secondary request onto the in-flight request
2/a. if a seconday request for the same offset was already chained to the
in-flight request, then just copy the contents of the page and discard
the new secondary request. This makes sure that for each page will
have at most two requests associated with it
3. when the in-flight request finished, send off all secondary requests
chained onto it
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Checking against tmp-page indexes is not very useful, and results in one
(or rarely two) page requests. Which is not much of an improvement...
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
The patch fixes a race between ftruncate(2), mmap-ed write and write(2):
1) An user makes a page dirty via mmap-ed write.
2) The user performs shrinking truncate(2) intended to purge the page.
3) Before fuse_do_setattr calls truncate_pagecache, the page goes to
writeback. fuse_writepages_fill attaches a new page to FUSE_WRITE request,
then releases the original page by end_page_writeback and unlock it.
4) fuse_do_setattr completes and successfully returns. Since now, i_mutex
is free.
5) Ordinary write(2) extends i_size back to cover the page. Note that
fuse_send_write_pages do wait for fuse writeback, but for another
page->index.
6) fuse_writepages_fill attaches more pages to the request (if any), then
fuse_writepages_send is eventually called. It is supposed to crop
inarg->size of the request, but it doesn't because i_size has already been
extended back.
Moving end_page_writeback behind fuse_writepages_send guarantees that
__fuse_release_nowrite (called from fuse_do_setattr) will crop inarg->size
of the request before write(2) gets the chance to extend i_size.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
The .writepages one is required to make each writeback request carry more than
one page on it. The patch enables optimized behaviour unconditionally,
i.e. mmap-ed writes will benefit from the patch even if fc->writeback_cache=0.
[SzM: simplify, add comments]
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Don't bug if there's no writable files found for page writeback. If ever
this is triggered, a WARN_ON helps debugging it much better then a BUG_ON.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Lock the page in fuse_page_mkwrite() to protect against a race with
fuse_writepage() where the page is redirtied before the actual writeback
begins.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
The .writepages callback will issue writeback requests with more than one
page aboard. Make existing end/check code be aware of this.
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
There will be a .writepageS callback implementation which will need to
get a fuse_file out of a fuse_inode, thus make a helper for this.
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Doing dput(parent) is not valid in RCU walk mode. In RCU mode it would
probably be okay to update the parent flags, but it's actually not
necessary most of the time...
So only set the FUSE_I_ADVISE_RDPLUS flag on the parent when the entry was
recently initialized by READDIRPLUS.
This is achieved by setting FUSE_I_INIT_RDPLUS on entries added by
READDIRPLUS and only dropping out of RCU mode if this flag is set.
FUSE_I_INIT_RDPLUS is cleared once the FUSE_I_ADVISE_RDPLUS flag is set in
the parent.
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
If revalidate finds an invalid dentry in RCU walk mode, let the VFS deal
with it instead of calling check_submounts_and_drop() which is not prepared
for being called from RCU walk.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
A former patch introducing FUSE_I_SIZE_UNSTABLE flag provided detailed
description of races between ftruncate and anyone who can extend i_size:
> 1. As in the previous scenario fuse_dentry_revalidate() discovered that i_size
> changed (due to our own fuse_do_setattr()) and is going to call
> truncate_pagecache() for some 'new_size' it believes valid right now. But by
> the time that particular truncate_pagecache() is called ...
> 2. fuse_do_setattr() returns (either having called truncate_pagecache() or
> not -- it doesn't matter).
> 3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
> 4. mmap-ed write makes a page in the extended region dirty.
This patch adds necessary bits to fuse_file_fallocate() to protect from that
race.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
The patch fixes a race between mmap-ed write and fallocate(PUNCH_HOLE):
1) An user makes a page dirty via mmap-ed write.
2) The user performs fallocate(2) with mode == PUNCH_HOLE|KEEP_SIZE
and <offset, size> covering the page.
3) Before truncate_pagecache_range call from fuse_file_fallocate,
the page goes to write-back. The page is fully processed by fuse_writepage
(including end_page_writeback on the page), but fuse_flush_writepages did
nothing because fi->writectr < 0.
4) truncate_pagecache_range is called and fuse_file_fallocate is finishing
by calling fuse_release_nowrite. The latter triggers processing queued
write-back request which will write stale data to the hole soon.
Changed in v2 (thanks to Brian for suggestion):
- Do not truncate page cache until FUSE_FALLOCATE succeeded. Otherwise,
we can end up in returning -ENOTSUPP while user data is already punched
from page cache. Use filemap_write_and_wait_range() instead.
Changed in v3 (thanks to Miklos for suggestion):
- fuse_wait_on_writeback() is prone to livelocks; use fuse_set_nowrite()
instead. So far as we need a dirty-page barrier only, fuse_sync_writes()
should be enough.
- rebased to for-linus branch of fuse.git
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
truncate_pagecache() doesn't care about old size since commit
cedabed49b ("vfs: Fix vmtruncate() regression"). Let's drop it.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The feature prevents mistrusted filesystems (ie: FUSE mounts created by
unprivileged users) to grow a large number of dirty pages before
throttling. For such filesystems balance_dirty_pages always check bdi
counters against bdi limits. I.e. even if global "nr_dirty" is under
"freerun", it's not allowed to skip bdi checks. The only use case for now
is fuse: it sets bdi max_ratio to 1% by default and system administrators
are supposed to expect that this limit won't be exceeded.
The feature is on if a BDI is marked by BDI_CAP_STRICTLIMIT flag. A
filesystem may set the flag when it initializes its BDI.
The problematic scenario comes from the fact that nobody pays attention to
the NR_WRITEBACK_TEMP counter (i.e. number of pages under fuse
writeback). The implementation of fuse writeback releases original page
(by calling end_page_writeback) almost immediately. A fuse request queued
for real processing bears a copy of original page. Hence, if userspace
fuse daemon doesn't finalize write requests in timely manner, an
aggressive mmap writer can pollute virtually all memory by those temporary
fuse page copies. They are carefully accounted in NR_WRITEBACK_TEMP, but
nobody cares.
To make further explanations shorter, let me use "NR_WRITEBACK_TEMP
problem" as a shortcut for "a possibility of uncontrolled grow of amount
of RAM consumed by temporary pages allocated by kernel fuse to process
writeback".
The problem was very easy to reproduce. There is a trivial example
filesystem implementation in fuse userspace distribution: fusexmp_fh.c. I
added "sleep(1);" to the write methods, then recompiled and mounted it.
Then created a huge file on the mount point and run a simple program which
mmap-ed the file to a memory region, then wrote a data to the region. An
hour later I observed almost all RAM consumed by fuse writeback. Since
then some unrelated changes in kernel fuse made it more difficult to
reproduce, but it is still possible now.
Putting this theoretical happens-in-the-lab thing aside, there is another
thing that really hurts real world (FUSE) users. This is write-through
page cache policy FUSE currently uses. I.e. handling write(2), kernel
fuse populates page cache and flushes user data to the server
synchronously. This is excessively suboptimal. Pavel Emelyanov's patches
("writeback cache policy") solve the problem, but they also make resolving
NR_WRITEBACK_TEMP problem absolutely necessary. Otherwise, simply copying
a huge file to a fuse mount would result in memory starvation. Miklos,
the maintainer of FUSE, believes strictlimit feature the way to go.
And eventually putting FUSE topics aside, there is one more use-case for
strictlimit feature. Using a slow USB stick (mass storage) in a machine
with huge amount of RAM installed is a well-known pain. Let's make simple
computations. Assuming 64GB of RAM installed, existing implementation of
balance_dirty_pages will start throttling only after 9.6GB of RAM becomes
dirty (freerun == 15% of total RAM). So, the command "cp 9GB_file
/media/my-usb-storage/" may return in a few seconds, but subsequent
"umount /media/my-usb-storage/" will take more than two hours if effective
throughput of the storage is, to say, 1MB/sec.
After inclusion of strictlimit feature, it will be trivial to add a knob
(e.g. /sys/devices/virtual/bdi/x:y/strictlimit) to enable it on demand.
Manually or via udev rule. May be I'm wrong, but it seems to be quite a
natural desire to limit the amount of dirty memory for some devices we are
not fully trust (in the sense of sustainable throughput).
[akpm@linux-foundation.org: fix warning in page-writeback.c]
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull fuse bugfixes from Miklos Szeredi:
"Just a bunch of bugfixes"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: use list_for_each_entry() for list traversing
fuse: readdir: check for slash in names
fuse: hotfix truncate_pagecache() issue
fuse: invalidate inode attributes on xattr modification
fuse: postpone end_page_writeback() in fuse_writepage_locked()
Drop a subtree when we find that it has moved or been delated. This can be
done as long as there are no submounts under this location.
If the directory was moved and we come across the same directory in a
future lookup it will be reconnected by d_materialise_unique().
Signed-off-by: Anand Avati <avati@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
On errors unrelated to the filesystem's state (ENOMEM, ENOTCONN) return the
error itself from ->d_revalidate() insted of returning zero (invalid).
Also make a common label for invalidating the dentry. This will be used by
the next patch.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Use d_materialise_unique() instead of d_splice_alias(). This allows dentry
subtrees to be moved to a new place if there moved, even if something is
referencing a dentry in the subtree (open fd, cwd, etc..).
This will also allow us to drop a subtree if it is found to be replaced by
something else. In this case the disconnected subtree can later be
reconnected to its new location.
d_materialise_unique() ensures that a directory entry only ever has one
alias. We keep fc->inst_mutex around the calls for d_materialise_unique()
on directories to prevent a race with mkdir "stealing" the inode.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Userspace can add names containing a slash character to the directory
listing. Don't allow this as it could cause all sorts of trouble.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
The way how fuse calls truncate_pagecache() from fuse_change_attributes()
is completely wrong. Because, w/o i_mutex held, we never sure whether
'oldsize' and 'attr->size' are valid by the time of execution of
truncate_pagecache(inode, oldsize, attr->size). In fact, as soon as we
released fc->lock in the middle of fuse_change_attributes(), we completely
loose control of actions which may happen with given inode until we reach
truncate_pagecache. The list of potentially dangerous actions includes
mmap-ed reads and writes, ftruncate(2) and write(2) extending file size.
The typical outcome of doing truncate_pagecache() with outdated arguments
is data corruption from user point of view. This is (in some sense)
acceptable in cases when the issue is triggered by a change of the file on
the server (i.e. externally wrt fuse operation), but it is absolutely
intolerable in scenarios when a single fuse client modifies a file without
any external intervention. A real life case I discovered by fsx-linux
looked like this:
1. Shrinking ftruncate(2) comes to fuse_do_setattr(). The latter sends
FUSE_SETATTR to the server synchronously, but before getting fc->lock ...
2. fuse_dentry_revalidate() is asynchronously called. It sends FUSE_LOOKUP
to the server synchronously, then calls fuse_change_attributes(). The
latter updates i_size, releases fc->lock, but before comparing oldsize vs
attr->size..
3. fuse_do_setattr() from the first step proceeds by acquiring fc->lock and
updating attributes and i_size, but now oldsize is equal to
outarg.attr.size because i_size has just been updated (step 2). Hence,
fuse_do_setattr() returns w/o calling truncate_pagecache().
4. As soon as ftruncate(2) completes, the user extends file size by
write(2) making a hole in the middle of file, then reads data from the hole
either by read(2) or mmap-ed read. The user expects to get zero data from
the hole, but gets stale data because truncate_pagecache() is not executed
yet.
The scenario above illustrates one side of the problem: not truncating the
page cache even though we should. Another side corresponds to truncating
page cache too late, when the state of inode changed significantly.
Theoretically, the following is possible:
1. As in the previous scenario fuse_dentry_revalidate() discovered that
i_size changed (due to our own fuse_do_setattr()) and is going to call
truncate_pagecache() for some 'new_size' it believes valid right now. But
by the time that particular truncate_pagecache() is called ...
2. fuse_do_setattr() returns (either having called truncate_pagecache() or
not -- it doesn't matter).
3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
4. mmap-ed write makes a page in the extended region dirty.
The result will be the lost of data user wrote on the fourth step.
The patch is a hotfix resolving the issue in a simplistic way: let's skip
dangerous i_size update and truncate_pagecache if an operation changing
file size is in progress. This simplistic approach looks correct for the
cases w/o external changes. And to handle them properly, more sophisticated
and intrusive techniques (e.g. NFS-like one) would be required. I'd like to
postpone it until the issue is well discussed on the mailing list(s).
Changed in v2:
- improved patch description to cover both sides of the issue.
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
Calls like setxattr and removexattr result in updation of ctime.
Therefore invalidate inode attributes to force a refresh.
Signed-off-by: Anand Avati <avati@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
The patch fixes a race between ftruncate(2), mmap-ed write and write(2):
1) An user makes a page dirty via mmap-ed write.
2) The user performs shrinking truncate(2) intended to purge the page.
3) Before fuse_do_setattr calls truncate_pagecache, the page goes to
writeback. fuse_writepage_locked fills FUSE_WRITE request and releases
the original page by end_page_writeback.
4) fuse_do_setattr() completes and successfully returns. Since now, i_mutex
is free.
5) Ordinary write(2) extends i_size back to cover the page. Note that
fuse_send_write_pages do wait for fuse writeback, but for another
page->index.
6) fuse_writepage_locked proceeds by queueing FUSE_WRITE request.
fuse_send_writepage is supposed to crop inarg->size of the request,
but it doesn't because i_size has already been extended back.
Moving end_page_writeback to the end of fuse_writepage_locked fixes the
race because now the fact that truncate_pagecache is successfully returned
infers that fuse_writepage_locked has already called end_page_writeback.
And this, in turn, infers that fuse_flush_writepages has already called
fuse_send_writepage, and the latter used valid (shrunk) i_size. write(2)
could not extend it because of i_mutex held by ftruncate(2).
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org
The dev_attrs field of struct class is going away soon, dev_groups
should be used instead. This converts the cuse class code to use the
correct field.
Acked-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fuse does instantiation slightly differently from NFS/CIFS which use
d_materialise_unique().
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Add sanity checks before adding or updating an entry with data received
from readdirplus.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
In case d_lookup() returns a dentry with d_inode == NULL, the dentry is not
returned with dput(). This results in triggering a BUG() in
shrink_dcache_for_umount_subtree():
BUG: Dentry ...{i=0,n=...} still in use (1) [unmount of fuse fuse]
[SzM: need to d_drop() as well]
Reported-by: Justin Clift <jclift@redhat.com>
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Brian Foster <bfoster@redhat.com>
Tested-by: Niels de Vos <ndevos@redhat.com>
CC: stable@vger.kernel.org
The global variable num_physpages is scheduled to be removed, so use
totalram_pages instead of num_physpages at runtime.
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull second set of VFS changes from Al Viro:
"Assorted f_pos race fixes, making do_splice_direct() safe to call with
i_mutex on parent, O_TMPFILE support, Jeff's locks.c series,
->d_hash/->d_compare calling conventions changes from Linus, misc
stuff all over the place."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (63 commits)
Document ->tmpfile()
ext4: ->tmpfile() support
vfs: export lseek_execute() to modules
lseek_execute() doesn't need an inode passed to it
block_dev: switch to fixed_size_llseek()
cpqphp_sysfs: switch to fixed_size_llseek()
tile-srom: switch to fixed_size_llseek()
proc_powerpc: switch to fixed_size_llseek()
ubi/cdev: switch to fixed_size_llseek()
pci/proc: switch to fixed_size_llseek()
isapnp: switch to fixed_size_llseek()
lpfc: switch to fixed_size_llseek()
locks: give the blocked_hash its own spinlock
locks: add a new "lm_owner_key" lock operation
locks: turn the blocked_list into a hashtable
locks: convert fl_link to a hlist_node
locks: avoid taking global lock if possible when waking up blocked waiters
locks: protect most of the file_lock handling with i_lock
locks: encapsulate the fl_link list handling
locks: make "added" in __posix_lock_file a bool
...
Pull VFS patches (part 1) from Al Viro:
"The major change in this pile is ->readdir() replacement with
->iterate(), dealing with ->f_pos races in ->readdir() instances for
good.
There's a lot more, but I'd prefer to split the pull request into
several stages and this is the first obvious cutoff point."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (67 commits)
[readdir] constify ->actor
[readdir] ->readdir() is gone
[readdir] convert ecryptfs
[readdir] convert coda
[readdir] convert ocfs2
[readdir] convert fatfs
[readdir] convert xfs
[readdir] convert btrfs
[readdir] convert hostfs
[readdir] convert afs
[readdir] convert ncpfs
[readdir] convert hfsplus
[readdir] convert hfs
[readdir] convert befs
[readdir] convert cifs
[readdir] convert freevxfs
[readdir] convert fuse
[readdir] convert hpfs
reiserfs: switch reiserfs_readdir_dentry to inode
reiserfs: is_privroot_deh() needs only directory inode, actually
...
Changing size of a file on server and local update (fuse_write_update_size)
should be always protected by inode->i_mutex. Otherwise a race like this is
possible:
1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE).
fuse_file_fallocate() sends FUSE_FALLOCATE request to the server.
2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr()
sends shrinking FUSE_SETATTR request to the server and updates local i_size
by i_size_write(inode, outarg.attr.size).
3. Process 'A' resumes execution of fuse_file_fallocate() and calls
fuse_write_update_size(inode, offset + length). But 'offset + length' was
obsoleted by ftruncate from previous step.
Changed in v2 (thanks Brian and Anand for suggestions):
- made relation between mutex_lock() and fuse_set_nowrite(inode) more
explicit and clear.
- updated patch description to use ftruncate(2) in example
Signed-off-by: Maxim V. Patlasov <MPatlasov@parallels.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
The bug was introduced with async_dio feature: trying to optimize short reads,
we cut number-of-bytes-to-read to i_size boundary. Hence the following example:
truncate --size=300 /mnt/file
dd if=/mnt/file of=/dev/null iflag=direct
led to FUSE_READ request of 300 bytes size. This turned out to be problem
for userspace fuse implementations who rely on assumption that kernel fuse
does not change alignment of request from client FS.
The patch turns off the optimization if async_dio is disabled. And, if it's
enabled, the patch fixes adjustment of number-of-bytes-to-read to preserve
alignment.
Note, that we cannot throw out short read optimization entirely because
otherwise a direct read of a huge size issued on a tiny file would generate
a huge amount of fuse requests and most of them would be ACKed by userspace
with zero bytes read.
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
If request submission fails for an async request (i.e.,
get_user_pages() returns -ERESTARTSYS), we currently skip the
-EIOCBQUEUED return and drop into wait_for_sync_kiocb() forever.
Avoid this by always returning -EIOCBQUEUED for async requests. If
an error occurs, the error is passed into fuse_aio_complete(),
returned via aio_complete() and thus propagated to userspace via
io_getevents().
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Fix bug introduced by commit 4582a4ab2a "FUSE: Adapt readdirplus to application
usage patterns".
We need to check for a positive dentry; negative dentries are not added by
readdirplus. Secondly we need to advise the use of readdirplus on the *parent*,
otherwise the whole thing is useless. Thirdly all this is only relevant if
"readdirplus_auto" mode is selected by the filesystem.
We advise the use of readdirplus only if the dentry was still valid. If we had
to redo the lookup then there was no use in doing the -plus version.
Reported-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: Feng Shuo <steve.shuo.feng@gmail.com>
CC: stable@vger.kernel.org
An fallocate request without FALLOC_FL_KEEP_SIZE set can extend the
size of a file. Update the inode size after a successful fallocate.
Also invalidate the inode attributes after a successful fallocate
to ensure we pick up the latest attribute values (i.e., i_blocks).
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
fuse supports hole punch via the fallocate() FALLOC_FL_PUNCH_HOLE
interface. When a hole punch is passed through, the page cache
is not cleared and thus allows reading stale data from the cache.
This is easily demonstrable (using FOPEN_KEEP_CACHE) by reading a
smallish random data file into cache, punching a hole and creating
a copy of the file. Drop caches or remount and observe that the
original file no longer matches the file copied after the hole
punch. The original file contains a zeroed range and the latter
file contains stale data.
Protect against writepage requests in progress and punch out the
associated page cache range after a successful client fs hole
punch.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Commit 8b41e671 introduced explicit background checking for fuse_req
structures with BUG_ON() checks for the appropriate type of request in
in the associated send functions. Commit bcba24cc introduced the ability
to send dio requests as background requests but does not update the
request allocation based on the type of I/O request. As a result, a
BUG_ON() triggers in the fuse_request_send_background() background path if
an async I/O is sent.
Allocate a request based on the async state of the fuse_io_priv to avoid
the BUG.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Merge more incoming from Andrew Morton:
- Various fixes which were stalled or which I picked up recently
- A large rotorooting of the AIO code. Allegedly to improve
performance but I don't really have good performance numbers (I might
have lost the email) and I can't raise Kent today. I held this out
of 3.9 and we could give it another cycle if it's all too late/scary.
I ended up taking only the first two thirds of the AIO rotorooting. I
left the percpu parts and the batch completion for later. - Linus
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (33 commits)
aio: don't include aio.h in sched.h
aio: kill ki_retry
aio: kill ki_key
aio: give shared kioctx fields their own cachelines
aio: kill struct aio_ring_info
aio: kill batch allocation
aio: change reqs_active to include unreaped completions
aio: use cancellation list lazily
aio: use flush_dcache_page()
aio: make aio_read_evt() more efficient, convert to hrtimers
wait: add wait_event_hrtimeout()
aio: refcounting cleanup
aio: make aio_put_req() lockless
aio: do fget() after aio_get_req()
aio: dprintk() -> pr_debug()
aio: move private stuff out of aio.h
aio: add kiocb_cancel()
aio: kill return value of aio_complete()
char: add aio_{read,write} to /dev/{null,zero}
aio: remove retry-based AIO
...
Pull fuse updates from Miklos Szeredi:
"This contains two patchsets from Maxim Patlasov.
The first reworks the request throttling so that only async requests
are throttled. Wakeup of waiting async requests is also optimized.
The second series adds support for async processing of direct IO which
optimizes direct IO and enables the use of the AIO userspace
interface."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: add flag to turn on async direct IO
fuse: truncate file if async dio failed
fuse: optimize short direct reads
fuse: enable asynchronous processing direct IO
fuse: make fuse_direct_io() aware about AIO
fuse: add support of async IO
fuse: move fuse_release_user_pages() up
fuse: optimize wake_up
fuse: implement exclusive wakeup for blocked_waitq
fuse: skip blocking on allocations of synchronous requests
fuse: add flag fc->initialized
fuse: make request allocations for background processing explicit
