In the previous commit, Richard Genoud fixed proc_root_readdir(), which
had lost the check for whether all of the non-process /proc entries had
been returned or not.
But that in turn exposed _another_ bug, namely that the original readdir
conversion patch had yet another problem: it had lost the return value
of proc_readdir_de(), so now checking whether it had completed
successfully or not didn't actually work right anyway.
This reinstates the non-zero return for the "end of base entries" that
had also gotten lost in commit f0c3b5093a ("[readdir] convert
procfs"). So now you get all the base entries *and* you get all the
process entries, regardless of getdents buffer size.
(Side note: the Linux "getdents" manual page actually has a nice example
application for testing getdents, which can be easily modified to use
different buffers. Who knew? Man-pages can be useful)
Reported-by: Emmanuel Benisty <benisty.e@gmail.com>
Reported-by: Marc Dionne <marc.c.dionne@gmail.com>
Cc: Richard Genoud <richard.genoud@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit f0c3b5093a ("[readdir] convert procfs") introduced a bug on the
listing of the proc file-system. The return value of proc_readdir()
isn't tested anymore in the proc_root_readdir function.
This lead to an "interesting" behaviour when we are using the getdents()
system call with a buffer too small: instead of failing, it returns the
first entries of /proc (enough to fill the given buffer), plus the PID
directories.
This is not triggered on glibc (as getdents is called with a 32KB
buffer), but on uclibc, the buffer size is only 1KB, thus some proc
entries are missing.
See https://lkml.org/lkml/2013/8/12/288 for more background.
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull gfs2 fixes from Steven Whitehouse:
"Out of these five patches, the one for ensuring that the number of
revokes is not exceeded, and the one for checking the glock is not
already held in gfs2_getxattr are the two most important. The latter
can be triggered by selinux.
The other three patches are very small and fix mostly fairly trivial
issues"
* git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-3.0-fixes:
GFS2: Check for glock already held in gfs2_getxattr
GFS2: alloc_workqueue() doesn't return an ERR_PTR
GFS2: don't overrun reserved revokes
GFS2: WQ_NON_REENTRANT is meaningless and going away
GFS2: Fix typo in gfs2_create_inode()
Since the introduction of atomic_open, gfs2_getxattr can be
called with the glock already held, so we need to allow for
this.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Reported-by: David Teigland <teigland@redhat.com>
Tested-by: David Teigland <teigland@redhat.com>
alloc_workqueue() returns a NULL on error, it doesn't return an ERR_PTR.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
When run during fsync, a gfs2_log_flush could happen between the
time when gfs2_ail_flush checked the number of blocks to revoke,
and when it actually started the transaction to do those revokes.
This occassionally caused it to need more revokes than it reserved,
causing gfs2 to crash.
Instead of just reserving enough revokes to handle the blocks that
currently need them, this patch makes gfs2_ail_flush reserve the
maximum number of revokes it can, without increasing the total number
of reserved log blocks. This patch also passes the number of reserved
revokes to __gfs2_ail_flush() so that it doesn't go over its limit
and cause a crash like we're seeing. Non-fsync calls to __gfs2_ail_flush
will still cause a BUG() necessary revokes are skipped.
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made
WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: cluster-devel@redhat.com
PTR_RET should be PTR_ERR
Reported-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)
iQIcBAABCAAGBQJSD2uJAAoJENNvdpvBGATwPwEP/R1Yu0UReTDVSmRwn8MGbk5O
M7QwPgUVnEdqr86v4qx7kqOmKtwSQKfSr7+07UGwEBVasPPI1ezXT5c2VAwz146z
5EClKIJoZoKIdWwM0NvUYxb7p5HgTLubho5RTsHmjOGIy37ju+5rFKZ44aHt9siY
J3w5v1EruHdDXwjyiZcIeHFUBGV34x9zPtIGy3yY06gEPAUMeEXShiH/Uj3EroKH
50PkwECBvqFuO4HpunhSYfNc3csTir2ZAx4judaV0s5ebyxzyZ398ql581q73mvP
m5KREYYVLQnN9VzCnsjLsnyZboh6XoTxmlmblNVOr0LihyKLS/Nof6pvrWEqgnBf
6NpR6Y8cPVUq+rhhXwFx/RIkVh2EIME0T5dZplr7fVaPxzI1ZKud8p18WifxMAix
y3rbdZiEA//OuH5u5XqV0/zv3aJUP7XjdT8dia5iq3FazFOdyT1VfVXzAfaXyqZk
JlFguSrOJbQe+vgk2gFLWLH8L4wsnGlSUv1AeDEboriushmZqYlAn10y6ENnM5yW
IMFNA6Wyz35MghsKMKV57H7B05VS8em6NGtHZVhTBt7JoiFn7PBvic/KcK/czpDy
W2Y8K8azhuscmQfa/RjuVDtwakbNwTu341e7hIUOy41qL/x9nNr07ZRAeF68Nesd
p4uRmJxLSW9PReYp9n4V
=OroQ
-----END PGP SIGNATURE-----
Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull jbd2 bug fixes from Ted Ts'o:
"Two jbd2 bug fixes, one of which is a regression fix"
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
jbd2: Fix oops in jbd2_journal_file_inode()
jbd2: Fix use after free after error in jbd2_journal_dirty_metadata()
Commit 0713ed0cde added
jbd2_journal_file_inode() call into ext4_block_zero_page_range().
However that function gets called from truncate path and thus inode
needn't have jinode attached - that happens in ext4_file_open() but
the file needn't be ever open since mount. Calling
jbd2_journal_file_inode() without jinode attached results in the oops.
We fix the problem by attaching jinode to inode also in ext4_truncate()
and ext4_punch_hole() when we are going to zero out partial blocks.
Reported-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Ben Tebulin reported:
"Since v3.7.2 on two independent machines a very specific Git
repository fails in 9/10 cases on git-fsck due to an SHA1/memory
failures. This only occurs on a very specific repository and can be
reproduced stably on two independent laptops. Git mailing list ran
out of ideas and for me this looks like some very exotic kernel issue"
and bisected the failure to the backport of commit 53a59fc67f ("mm:
limit mmu_gather batching to fix soft lockups on !CONFIG_PREEMPT").
That commit itself is not actually buggy, but what it does is to make it
much more likely to hit the partial TLB invalidation case, since it
introduces a new case in tlb_next_batch() that previously only ever
happened when running out of memory.
The real bug is that the TLB gather virtual memory range setup is subtly
buggered. It was introduced in commit 597e1c3580 ("mm/mmu_gather:
enable tlb flush range in generic mmu_gather"), and the range handling
was already fixed at least once in commit e6c495a96c ("mm: fix the TLB
range flushed when __tlb_remove_page() runs out of slots"), but that fix
was not complete.
The problem with the TLB gather virtual address range is that it isn't
set up by the initial tlb_gather_mmu() initialization (which didn't get
the TLB range information), but it is set up ad-hoc later by the
functions that actually flush the TLB. And so any such case that forgot
to update the TLB range entries would potentially miss TLB invalidates.
Rather than try to figure out exactly which particular ad-hoc range
setup was missing (I personally suspect it's the hugetlb case in
zap_huge_pmd(), which didn't have the same logic as zap_pte_range()
did), this patch just gets rid of the problem at the source: make the
TLB range information available to tlb_gather_mmu(), and initialize it
when initializing all the other tlb gather fields.
This makes the patch larger, but conceptually much simpler. And the end
result is much more understandable; even if you want to play games with
partial ranges when invalidating the TLB contents in chunks, now the
range information is always there, and anybody who doesn't want to
bother with it won't introduce subtle bugs.
Ben verified that this fixes his problem.
Reported-bisected-and-tested-by: Ben Tebulin <tebulin@googlemail.com>
Build-testing-by: Stephen Rothwell <sfr@canb.auug.org.au>
Build-testing-by: Richard Weinberger <richard.weinberger@gmail.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Recently we met quite a lot of random kernel panic issues after enabling
CONFIG_PROC_PAGE_MONITOR. After debuggind we found this has something
to do with following bug in pagemap:
In struct pagemapread:
struct pagemapread {
int pos, len;
pagemap_entry_t *buffer;
bool v2;
};
pos is number of PM_ENTRY_BYTES in buffer, but len is the size of
buffer, it is a mistake to compare pos and len in add_page_map() for
checking buffer is full or not, and this can lead to buffer overflow and
random kernel panic issue.
Correct len to be total number of PM_ENTRY_BYTES in buffer.
[akpm@linux-foundation.org: document pagemapread.pos and .len units, fix PM_ENTRY_BYTES definition]
Signed-off-by: Yonghua Zheng <younghua.zheng@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since ocfs2_cow_file_pos will invoke ocfs2_refcount_icow with a NULL as
the struct file pointer, it finally result in a null pointer dereference
in ocfs2_duplicate_clusters_by_page.
This patch replace file pointer with inode pointer in
cow_duplicate_clusters to fix this issue.
[jeff.liu@oracle.com: rebased patch against linux-next tree]
Signed-off-by: Tiger Yang <tiger.yang@oracle.com>
Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Acked-by: Tao Ma <tm@tao.ma>
Tested-by: David Weber <wb@munzinger.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Revert commit 40bd62eb7f ("fs/ocfs2/journal.h: add bits_wanted while
calculating credits in ocfs2_calc_extend_credits").
Unfortunately this change broke fallocate even if there is insufficient
disk space for the preallocation, which is a serious problem.
# df -h
/dev/sda8 22G 1.2G 21G 6% /ocfs2
# fallocate -o 0 -l 200M /ocfs2/testfile
fallocate: /ocfs2/test: fallocate failed: No space left on device
and a kernel warning:
CPU: 3 PID: 3656 Comm: fallocate Tainted: G W O 3.11.0-rc3 #2
Call Trace:
dump_stack+0x77/0x9e
warn_slowpath_common+0xc4/0x110
warn_slowpath_null+0x2a/0x40
start_this_handle+0x6c/0x640 [jbd2]
jbd2__journal_start+0x138/0x300 [jbd2]
jbd2_journal_start+0x23/0x30 [jbd2]
ocfs2_start_trans+0x166/0x300 [ocfs2]
__ocfs2_extend_allocation+0x38f/0xdb0 [ocfs2]
ocfs2_allocate_unwritten_extents+0x3c9/0x520
__ocfs2_change_file_space+0x5e0/0xa60 [ocfs2]
ocfs2_fallocate+0xb1/0xe0 [ocfs2]
do_fallocate+0x1cb/0x220
SyS_fallocate+0x6f/0xb0
system_call_fastpath+0x16/0x1b
JBD2: fallocate wants too many credits (51216 > 4381)
Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Dave has reported the following lockdep splat:
=================================
[ INFO: inconsistent lock state ]
3.11.0-rc1+ #9 Not tainted
---------------------------------
inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
kswapd0/49 [HC0[0]:SC0[0]:HE1:SE1] takes:
(&mapping->i_mmap_mutex){+.+.?.}, at: [<c114971b>] page_referenced+0x87/0x5e3
{RECLAIM_FS-ON-W} state was registered at:
mark_held_locks+0x81/0xe7
lockdep_trace_alloc+0x5e/0xbc
__alloc_pages_nodemask+0x8b/0x9b6
__get_free_pages+0x20/0x31
get_zeroed_page+0x12/0x14
__pmd_alloc+0x1c/0x6b
huge_pmd_share+0x265/0x283
huge_pte_alloc+0x5d/0x71
hugetlb_fault+0x7c/0x64a
handle_mm_fault+0x255/0x299
__do_page_fault+0x142/0x55c
do_page_fault+0xd/0x16
error_code+0x6c/0x74
irq event stamp: 3136917
hardirqs last enabled at (3136917): _raw_spin_unlock_irq+0x27/0x50
hardirqs last disabled at (3136916): _raw_spin_lock_irq+0x15/0x78
softirqs last enabled at (3136180): __do_softirq+0x137/0x30f
softirqs last disabled at (3136175): irq_exit+0xa8/0xaa
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&mapping->i_mmap_mutex);
<Interrupt>
lock(&mapping->i_mmap_mutex);
*** DEADLOCK ***
no locks held by kswapd0/49.
stack backtrace:
CPU: 1 PID: 49 Comm: kswapd0 Not tainted 3.11.0-rc1+ #9
Hardware name: Dell Inc. Precision WorkStation 490 /0DT031, BIOS A08 04/25/2008
Call Trace:
dump_stack+0x4b/0x79
print_usage_bug+0x1d9/0x1e3
mark_lock+0x1e0/0x261
__lock_acquire+0x623/0x17f2
lock_acquire+0x7d/0x195
mutex_lock_nested+0x6c/0x3a7
page_referenced+0x87/0x5e3
shrink_page_list+0x3d9/0x947
shrink_inactive_list+0x155/0x4cb
shrink_lruvec+0x300/0x5ce
shrink_zone+0x53/0x14e
kswapd+0x517/0xa75
kthread+0xa8/0xaa
ret_from_kernel_thread+0x1b/0x28
which is a false positive caused by hugetlb pmd sharing code which
allocates a new pmd from withing mapping->i_mmap_mutex. If this
allocation causes reclaim then the lockdep detector complains that we
might self-deadlock.
This is not correct though, because hugetlb pages are not reclaimable so
their mapping will be never touched from the reclaim path.
The patch tells lockup detector that hugetlb i_mmap_mutex is special by
assigning it a separate lockdep class so it won't report possible
deadlocks on unrelated mappings.
[peterz@infradead.org: comment for annotation]
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andy reported that if file page get reclaimed we lose the soft-dirty bit
if it was there, so save _PAGE_BIT_SOFT_DIRTY bit when page address get
encoded into pte entry. Thus when #pf happens on such non-present pte
we can restore it back.
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andy Lutomirski reported that if a page with _PAGE_SOFT_DIRTY bit set
get swapped out, the bit is getting lost and no longer available when
pte read back.
To resolve this we introduce _PTE_SWP_SOFT_DIRTY bit which is saved in
pte entry for the page being swapped out. When such page is to be read
back from a swap cache we check for bit presence and if it's there we
clear it and restore the former _PAGE_SOFT_DIRTY bit back.
One of the problem was to find a place in pte entry where we can save
the _PTE_SWP_SOFT_DIRTY bit while page is in swap. The _PAGE_PSE was
chosen for that, it doesn't intersect with swap entry format stored in
pte.
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull CIFS fixes from Steve French:
"A set of small cifs fixes, including 3 relating to symlink handling"
* 'for-next' of git://git.samba.org/sfrench/cifs-2.6:
cifs: don't instantiate new dentries in readdir for inodes that need to be revalidated immediately
cifs: set sb->s_d_op before calling d_make_root()
cifs: fix bad error handling in crypto code
cifs: file: initialize oparms.reconnect before using it
Do not attempt to do cifs operations reading symlinks with SMB2
cifs: extend the buffer length enought for sprintf() using
so that if ext4 is built as a module, to allow it to be unloaded.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)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=NuDG
-----END PGP SIGNATURE-----
Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull more ext4 bugfixes from Ted Ts'o:
"A number of miscellaneous ext4 bugs fixes for v3.11, including a fix
so that if ext4 is built as a module, to allow it to be unloaded"
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
ext4: flush the extent status cache during EXT4_IOC_SWAP_BOOT
ext4: fix mount/remount error messages for incompatible mount options
ext4: allow the mount options nodelalloc and data=journal
When jbd2_journal_dirty_metadata() returns error,
__ext4_handle_dirty_metadata() stops the handle. However callers of this
function do not count with that fact and still happily used now freed
handle. This use after free can result in various issues but very likely
we oops soon.
The motivation of adding __ext4_journal_stop() into
__ext4_handle_dirty_metadata() in commit 9ea7a0df seems to be only to
improve error reporting. So replace __ext4_journal_stop() with
ext4_journal_abort_handle() which was there before that commit and add
WARN_ON_ONCE() to dump stack to provide useful information.
Reported-by: Sage Weil <sage@inktank.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org # 3.2+
Previously we weren't swapping only some of the extent_status LRU
fields during the processing of the EXT4_IOC_SWAP_BOOT ioctl. The
much safer thing to do is to just completely flush the extent status
tree when doing the swap.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Zheng Liu <gnehzuil.liu@gmail.com>
Cc: stable@vger.kernel.org
Pull btrfs fixes from Chris Mason:
"These are assorted fixes, mostly from Josef nailing down xfstests
runs. Zach also has a long standing fix for problems with readdir
wrapping f_pos (or ctx->pos)
These patches were spread out over different bases, so I rebased
things on top of rc4 and retested overnight"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
btrfs: don't loop on large offsets in readdir
Btrfs: check to see if root_list is empty before adding it to dead roots
Btrfs: release both paths before logging dir/changed extents
Btrfs: allow splitting of hole em's when dropping extent cache
Btrfs: make sure the backref walker catches all refs to our extent
Btrfs: fix backref walking when we hit a compressed extent
Btrfs: do not offset physical if we're compressed
Btrfs: fix extent buffer leak after backref walking
Btrfs: fix a bug of snapshot-aware defrag to make it work on partial extents
btrfs: fix file truncation if FALLOC_FL_KEEP_SIZE is specified
- Stable patch for lockd to fix Oopses due to inappropriate calls to
utsname()->nodename
- Stable patches for sunrpc to fix Oopses on shutdown when using
AF_LOCAL sockets with rpcbind
- Fix memory leak and error checking issues in nfs4_proc_lookup_mountpoint
- Fix a regression with the sync mount option failing to work for nfs4 mounts
- Fix a writeback performance issue when doing cache invalidation
- Remove an incorrect call to nfs_setsecurity in nfs_fhget
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.13 (GNU/Linux)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=W12x
-----END PGP SIGNATURE-----
Merge tag 'nfs-for-3.11-4' of git://git.linux-nfs.org/projects/trondmy/linux-nfs
Pull NFS client bugfixes from Trond Myklebust:
- Stable patch for lockd to fix Oopses due to inappropriate calls to
utsname()->nodename
- Stable patches for sunrpc to fix Oopses on shutdown when using
AF_LOCAL sockets with rpcbind
- Fix memory leak and error checking issues in nfs4_proc_lookup_mountpoint
- Fix a regression with the sync mount option failing to work for nfs4
mounts
- Fix a writeback performance issue when doing cache invalidation
- Remove an incorrect call to nfs_setsecurity in nfs_fhget
* tag 'nfs-for-3.11-4' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
NFSv4: Fix up nfs4_proc_lookup_mountpoint
NFS: Remove unnecessary call to nfs_setsecurity in nfs_fhget()
NFSv4: Fix the sync mount option for nfs4 mounts
NFS: Fix writeback performance issue on cache invalidation
SUNRPC: If the rpcbind channel is disconnected, fail the call to unregister
SUNRPC: Don't auto-disconnect from the local rpcbind socket
LOCKD: Don't call utsname()->nodename from nlmclnt_setlockargs
Pull nfsd fixes from Bruce Fields:
"Some fixes for a 4.1 feature that in retrospect probably should have
waited for 3.12.... But it appears to be working now"
* 'for-3.11' of git://linux-nfs.org/~bfields/linux:
nfsd: Fix SP4_MACH_CRED negotiation in EXCHANGE_ID
nfsd4: Fix MACH_CRED NULL dereference
When btrfs readdir() hits the last entry it sets the readdir offset to a
huge value to stop buggy apps from breaking when the same name is
returned by readdir() with concurrent rename()s.
But unconditionally setting the offset to INT_MAX causes readdir() to
loop returning any entries with offsets past INT_MAX. It only takes a
few hours of constant file creation and removal to create entries past
INT_MAX.
So let's set the huge offset to LLONG_MAX if the last entry has already
overflowed 32bit loff_t. Without large offsets behaviour is identical.
With large offsets 64bit apps will work and 32bit apps will be no more
broken than they currently are if they see large offsets.
Signed-off-by: Zach Brown <zab@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
A user reported a panic when running with autodefrag and deleting snapshots.
This is because we could end up trying to add the root to the dead roots list
twice. To fix this check to see if we are empty before adding ourselves to the
dead roots list. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
The ceph guys tripped over this bug where we were still holding onto the
original path that we used to copy the inode with when logging. This is based
on Chris's fix which was reported to fix the problem. We need to drop the paths
in two cases anyway so just move the drop up so that we don't have duplicate
code. Thanks,
Cc: stable@vger.kernel.org
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
I noticed while running multi-threaded fsync tests that sometimes fsck would
complain about an improper gap. This happens because we fail to add a hole
extent to the file, which was happening when we'd split a hole EM because
btrfs_drop_extent_cache was just discarding the whole em instead of splitting
it. So this patch fixes this by allowing us to split a hole em properly, which
means that added holes actually get logged properly and we no longer see this
fsck error. Thankfully we're tolerant of these sort of problems so a user would
not see any adverse effects of this bug, other than fsck complaining. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Because we don't mess with the offset into the extent for compressed we will
properly find both extents for this case
[extent a][extent b][rest of extent a]
but because we already added a ref for the front half we won't add the inode
information for the second half. This causes us to leak that memory and not
print out the other offset when we do logical-resolve. So fix this by calling
ulist_add_merge and then add our eie to the existing entry if there is one.
With this patch we get both offsets out of logical-resolve. With this and the
other 2 patches I've sent we now pass btrfs/276 on my vm with compress-force=lzo
set. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
If you do btrfs inspect-internal logical-resolve on a compressed extent that has
been partly overwritten it won't find anything. This is because we try and
match the extent offset we've searched for based on the extent offset in the
data extent entry. However this doesn't work for compressed extents because the
offsets are for the uncompressed size, not the compressed size. So instead only
do this check if we are not compressed, that way we can get an actual entry for
the physical offset rather than nothing for compressed. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
xfstest btrfs/276 was freaking out on slower boxes partly because fiemap was
offsetting the physical based on the extent offset. This is perfectly fine with
uncompressed extents, however the extent offset is into the uncompressed area,
not the compressed. So we can return a physical value that isn't at all within
the area we have allocated on disk. Fix this by returning the start of the
extent if it is compressed no matter what the offset. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
commit 47fb091fb787420cd195e66f162737401cce023f(Btrfs: fix unlock after free on rewinded tree blocks)
takes an extra increment on the reference of allocated dummy extent buffer, so now we
cannot free this dummy one, and end up with extent buffer leak.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
For partial extents, snapshot-aware defrag does not work as expected,
since
a) we use the wrong logical offset to search for parents, which should be
disk_bytenr + extent_offset, not just disk_bytenr,
b) 'offset' returned by the backref walking just refers to key.offset, not
the 'offset' stored in btrfs_extent_data_ref which is
(key.offset - extent_offset).
The reproducer:
$ mkfs.btrfs sda
$ mount sda /mnt
$ btrfs sub create /mnt/sub
$ for i in `seq 5 -1 1`; do dd if=/dev/zero of=/mnt/sub/foo bs=5k count=1 seek=$i conv=notrunc oflag=sync; done
$ btrfs sub snap /mnt/sub /mnt/snap1
$ btrfs sub snap /mnt/sub /mnt/snap2
$ sync; btrfs filesystem defrag /mnt/sub/foo;
$ umount /mnt
$ btrfs-debug-tree sda (Here we can check whether the defrag operation is snapshot-awared.
This addresses the above two problems.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Create a small file and fallocate it to a big size with
FALLOC_FL_KEEP_SIZE option, then truncate it back to the
small size again, the disk free space is not changed back
in this case. i.e,
total 4
-rw-r--r-- 1 root root 512 Jun 28 11:35 test
Filesystem Size Used Avail Use% Mounted on
....
/dev/sdb1 8.0G 56K 7.2G 1% /mnt
-rw-r--r-- 1 root root 512 Jun 28 11:35 /mnt/test
Filesystem Size Used Avail Use% Mounted on
....
/dev/sdb1 8.0G 5.1G 2.2G 70% /mnt
Filesystem Size Used Avail Use% Mounted on
....
/dev/sdb1 8.0G 5.1G 2.2G 70% /mnt
With this fix, the truncated up space is back as:
Filesystem Size Used Avail Use% Mounted on
....
/dev/sdb1 8.0G 56K 7.2G 1% /mnt
Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
device_close()->recalc_sigpending() is not needed, sigprocmask() takes
care of TIF_SIGPENDING correctly.
And without ->siglock it is racy and wrong, it can wrongly clear
TIF_SIGPENDING and miss a signal.
But even with this patch device_close() is still buggy:
1. sigprocmask() should not be used, we have set_task_blocked(),
but this is minor.
2. We should never block SIGKILL or SIGSTOP, and this is what
the code tries to do.
3. This can't protect against SIGKILL or SIGSTOP anyway. Another
thread can do signal_wake_up(), say, do_signal_stop() or
complete_signal() or debugger.
4. sigprocmask(SIG_BLOCK, allsigs) doesn't necessarily clears
TIF_SIGPENDING, say, freezing() or ->jobctl.
5. device_write() looks equally wrong by the same reason.
Looks like, this tries to protect some wait_event_interruptible() logic
from signals, it should be turned into uninterruptible wait. Or we need
to implement something like signals_stop/start for such a use-case.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 5688978 ("ext4: improve handling of conflicting mount options")
introduced incorrect messages shown while choosing wrong mount options.
First of all, both cases of incorrect mount options,
"data=journal,delalloc" and "data=journal,dioread_nolock" result in
the same error message.
Secondly, the problem above isn't solved for remount option: the
mismatched parameter is simply ignored. Moreover, ext4_msg states
that remount with options "data=journal,delalloc" succeeded, which is
not true.
To fix it up, I added a simple check after parse_options() call to
ensure that data=journal and delalloc/dioread_nolock parameters are
not present at the same time.
Signed-off-by: Piotr Sarna <p.sarna@partner.samsung.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
Commit 26092bf ("ext4: use a table-driven handler for mount options")
wrongly disallows the specifying the mount options nodelalloc and
data=journal simultaneously. This is incorrect; it should have only
disallowed the combination of delalloc and data=journal
simultaneously.
Reported-by: Piotr Sarna <p.sarna@partner.samsung.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)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=xqB3
-----END PGP SIGNATURE-----
Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull ext4 bugfixes from Ted Ts'o.
Misc ext4 fixes, delayed by Ted moving mail servers and email getting
marked as spam due to bad spf records.
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
ext4: add WARN_ON to check the length of allocated blocks
ext4: fix retry handling in ext4_ext_truncate()
ext4: destroy ext4_es_cachep on module unload
ext4: make sure group number is bumped after a inode allocation race
Currently, we do not check the return value of client = rpc_clone_client(),
nor do we shut down the resulting cloned rpc_clnt in the case where a
NFS4ERR_WRONGSEC has caused nfs4_proc_lookup_common() to replace the
original value of 'client' (causing a memory leak).
Fix both issues and simplify the code by moving the call to
rpc_clone_client() until after nfs4_proc_lookup_common() has
done its business.
Reported-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
We only need to call it on the creation of the inode.
Reported-by: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Steve Dickson <SteveD@redhat.com>
Cc: Dave Quigley <dpquigl@davequigley.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
The sync mount option stopped working for NFSv4 mounts after commit
c02d7adf8c (NFSv4: Replace nfs4_path_walk() with
FS path lookup in a private namespace). If MS_SYNCHRONOUS is set in the
super_block that we're cloning from, then it should be set in the new
super_block as well.
Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
If a cache invalidation is triggered, and we happen to have a lot of
writebacks cached at the time, then the call to invalidate_inode_pages2()
will end up calling ->launder_page() on each and every dirty page in order
to sync its contents to disk, thus defeating write coalescing.
The following patch ensures that we try to sync the inode to disk before
calling invalidate_inode_pages2() so that we do the writeback as efficiently
as possible.
Reported-by: William Dauchy <william@gandi.net>
Reported-by: Pascal Bouchareine <pascal@gandi.net>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: William Dauchy <william@gandi.net>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
lead to race conditions between deleting an event and accessing an event
debugfs file. This included a fix to the debugfs system (acked by
Greg Kroah-Hartman). We think that all the holes have been patched and
hopefully we don't find more. I haven't marked all of them for stable
because I need to examine them more to figure out how far back some of
the changes need to go.
Along the way, some other fixes have been made. Alexander Z Lam fixed
some logic where the wrong buffer was being modifed.
Andrew Vagin found a possible corruption for machines that actually
allocate cpumask, as a reference to one was being zeroed out by mistake.
Dhaval Giani found a bad prototype when tracing is not configured.
And I not only had some changes to help Oleg, but also finally fixed
a long standing bug that Dave Jones and others have been hitting, where
a module unload and reload can cause the function tracing accounting
to get screwed up.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.14 (GNU/Linux)
iQEcBAABAgAGBQJR/7FvAAoJEOdOSU1xswtMCAgH/RpxS5mQcQnhrGfu1qnSk+3v
CyL1X9IkvgP5f+N59tbU3ZuE8Q3YQvTII35na38fgbHbwWrhYjLSvlf3Pwtre8zr
Rjm9b8zA6iSobHu3DyuuupzMsLE+SpBakVSmG6mi8izZyuCi0YHMZMnHTGNnW9Vv
YFqkfGgQQWMqiUHLcueetOqWAjR2JiJaLfr47rsRLNflF6dB2MbG/7YbYJ0TBk7E
hemVmR7JH7606eJZ6nR7bh/hYv0sL2SSqVVaOHO5nWFLFbI8CybpNVGcoD+nihZY
M7LrZT1C1mn3nKrfDhyXy4dwwx6wBON0fY23eJTHMVNnc0tvY1xqH52vTdPILWg=
=UfsE
-----END PGP SIGNATURE-----
Merge tag 'trace-fixes-3.11-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fixes from Steven Rostedt:
"Oleg Nesterov has been working hard in closing all the holes that can
lead to race conditions between deleting an event and accessing an
event debugfs file. This included a fix to the debugfs system (acked
by Greg Kroah-Hartman). We think that all the holes have been patched
and hopefully we don't find more. I haven't marked all of them for
stable because I need to examine them more to figure out how far back
some of the changes need to go.
Along the way, some other fixes have been made. Alexander Z Lam fixed
some logic where the wrong buffer was being modifed.
Andrew Vagin found a possible corruption for machines that actually
allocate cpumask, as a reference to one was being zeroed out by
mistake.
Dhaval Giani found a bad prototype when tracing is not configured.
And I not only had some changes to help Oleg, but also finally fixed a
long standing bug that Dave Jones and others have been hitting, where
a module unload and reload can cause the function tracing accounting
to get screwed up"
* tag 'trace-fixes-3.11-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Fix reset of time stamps during trace_clock changes
tracing: Make TRACE_ITER_STOP_ON_FREE stop the correct buffer
tracing: Fix trace_dump_stack() proto when CONFIG_TRACING is not set
tracing: Fix fields of struct trace_iterator that are zeroed by mistake
tracing/uprobes: Fail to unregister if probe event files are in use
tracing/kprobes: Fail to unregister if probe event files are in use
tracing: Add comment to describe special break case in probe_remove_event_call()
tracing: trace_remove_event_call() should fail if call/file is in use
debugfs: debugfs_remove_recursive() must not rely on list_empty(d_subdirs)
ftrace: Check module functions being traced on reload
ftrace: Consolidate some duplicate code for updating ftrace ops
tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private
tracing: Introduce remove_event_file_dir()
tracing: Change f_start() to take event_mutex and verify i_private != NULL
tracing: Change event_filter_read/write to verify i_private != NULL
tracing: Change event_enable/disable_read() to verify i_private != NULL
tracing: Turn event/id->i_private into call->event.type
- don't BUG_ON() when not SP4_NONE
- calculate recv and send reserve sizes correctly
Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
David reported that commit c2b93e06 (cifs: only set ops for inodes in
I_NEW state) caused a regression with mfsymlinks. Prior to that patch,
if a mfsymlink dentry was instantiated at readdir time, the inode would
get a new set of ops when it was revalidated. After that patch, this
did not occur.
This patch addresses this by simply skipping instantiating dentries in
the readdir codepath when we know that they will need to be immediately
revalidated. The next attempt to use that dentry will cause a new lookup
to occur (which is basically what we want to happen anyway).
Cc: <stable@vger.kernel.org>
Cc: "Stefan (metze) Metzmacher" <metze@samba.org>
Cc: Sachin Prabhu <sprabhu@redhat.com>
Reported-and-Tested-by: David McBride <dwm37@cam.ac.uk>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Firstly, nlmclnt_setlockargs can be called from a reclaimer thread, in
which case we're in entirely the wrong namespace.
Secondly, commit 8aac62706a (move
exit_task_namespaces() outside of exit_notify()) now means that
exit_task_work() is called after exit_task_namespaces(), which
triggers an Oops when we're freeing up the locks.
Fix this by ensuring that we initialise the nlm_host's rpc_client at mount
time, so that the cl_nodename field is initialised to the value of
utsname()->nodename that the net namespace uses. Then replace the
lockd callers of utsname()->nodename.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Toralf Förster <toralf.foerster@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Nix <nix@esperi.org.uk>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: stable@vger.kernel.org # 3.10.x
As comment in include/uapi/asm-generic/fcntl.h described, when
introducing new O_* bits, we need to check its uniqueness in
fcntl_init(). But __O_TMPFILE bit is missing. So fix it.
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Every now and then someone proposes a new flink syscall, and this spawns
a long discussion of whether it would be a security problem. I think
that this is missing the point: flink is *already* allowed without
privilege as long as /proc is mounted -- it's called AT_SYMLINK_FOLLOW.
Now that O_TMPFILE is here, the ability to create a file with O_TMPFILE,
write it, and link it in is very convenient. The only problem is that
it requires that /proc be mounted so that you can do:
linkat(AT_FDCWD, "/proc/self/fd/<tmpfd>", dfd, path, AT_SYMLINK_NOFOLLOW)
This sucks -- it's much nicer to do:
linkat(tmpfd, "", dfd, path, AT_EMPTY_PATH)
Let's allow it.
If this turns out to be excessively scary, it we could instead require
that the inode in question be I_LINKABLE, but this seems pointless given
the /proc situation
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Linus Torvalds