NFS: add barriers when testing for NFS_FSDATA_BLOCKED

[ Upstream commit 99bc9f2eb3f79a2b4296d9bf43153e1d10ca50d3 ]

dentry->d_fsdata is set to NFS_FSDATA_BLOCKED while unlinking or
renaming-over a f

NFS: add barriers when testing for NFS_FSDATA_BLOCKED

[ Upstream commit 99bc9f2eb3f79a2b4296d9bf43153e1d10ca50d3 ]

dentry->d_fsdata is set to NFS_FSDATA_BLOCKED while unlinking or
renaming-over a file to ensure that no open succeeds while the NFS
operation progressed on the server.

Setting dentry->d_fsdata to NFS_FSDATA_BLOCKED is done under ->d_lock
after checking the refcount is not elevated. Any attempt to open the
file (through that name) will go through lookp_open() which will take
->d_lock while incrementing the refcount, we can be sure that once the
new value is set, __nfs_lookup_revalidate() *will* see the new value and
will block.

We don't have any locking guarantee that when we set ->d_fsdata to NULL,
the wait_var_event() in __nfs_lookup_revalidate() will notice.
wait/wake primitives do NOT provide barriers to guarantee order. We
must use smp_load_acquire() in wait_var_event() to ensure we look at an
up-to-date value, and must use smp_store_release() before wake_up_var().

This patch adds those barrier functions and factors out
block_revalidate() and unblock_revalidate() far clarity.

There is also a hypothetical bug in that if memory allocation fails
(which never happens in practice) we might leave ->d_fsdata locked.
This patch adds the missing call to unblock_revalidate().

Reported-and-tested-by: Richard Kojedzinszky <richard+debian+bugreport@kojedz.in>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1071501
Fixes: 3c59366c207e ("NFS: don't unhash dentry during unlink/rename")
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

NFS: add barriers when testing for NFS_FSDATA_BLOCKED

[ Upstream commit 99bc9f2eb3f79a2b4296d9bf43153e1d10ca50d3 ]

dentry->d_fsdata is set to NFS_FSDATA_BLOCKED while unlinking or
renaming-over a f

NFS: add barriers when testing for NFS_FSDATA_BLOCKED

[ Upstream commit 99bc9f2eb3f79a2b4296d9bf43153e1d10ca50d3 ]

dentry->d_fsdata is set to NFS_FSDATA_BLOCKED while unlinking or
renaming-over a file to ensure that no open succeeds while the NFS
operation progressed on the server.

Setting dentry->d_fsdata to NFS_FSDATA_BLOCKED is done under ->d_lock
after checking the refcount is not elevated. Any attempt to open the
file (through that name) will go through lookp_open() which will take
->d_lock while incrementing the refcount, we can be sure that once the
new value is set, __nfs_lookup_revalidate() *will* see the new value and
will block.

We don't have any locking guarantee that when we set ->d_fsdata to NULL,
the wait_var_event() in __nfs_lookup_revalidate() will notice.
wait/wake primitives do NOT provide barriers to guarantee order. We
must use smp_load_acquire() in wait_var_event() to ensure we look at an
up-to-date value, and must use smp_store_release() before wake_up_var().

This patch adds those barrier functions and factors out
block_revalidate() and unblock_revalidate() far clarity.

There is also a hypothetical bug in that if memory allocation fails
(which never happens in practice) we might leave ->d_fsdata locked.
This patch adds the missing call to unblock_revalidate().

Reported-and-tested-by: Richard Kojedzinszky <richard+debian+bugreport@kojedz.in>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1071501
Fixes: 3c59366c207e ("NFS: don't unhash dentry during unlink/rename")
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

NFS: Use parent's objective cred in nfs_access_login_time()

[ Upstream commit a10a9233073d984b239e22358ba21825e27e2e88 ]

The subjective cred (task->cred) can potentially be overridden and
subsquent

NFS: Use parent's objective cred in nfs_access_login_time()

[ Upstream commit a10a9233073d984b239e22358ba21825e27e2e88 ]

The subjective cred (task->cred) can potentially be overridden and
subsquently freed in non-RCU context, which could lead to a panic if we
try to use it in cred_fscmp(). Use __task_cred(), which returns the
objective cred (task->real_cred) instead.

Fixes: 0eb43812c027 ("NFS: Clear the file access cache upon login")
Fixes: 5e9a7b9c2ea1 ("NFS: Fix up a sparse warning")

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

nfs: fix redundant readdir request after get eof

When a directory contains 17 files (except . and ..), nfs client sends
a redundant readdir request after get eof.

A simple reproduce,
At NFS server,

nfs: fix redundant readdir request after get eof

When a directory contains 17 files (except . and ..), nfs client sends
a redundant readdir request after get eof.

A simple reproduce,
At NFS server, create a directory with 17 files under exported directory.
# mkdir test
# cd test
# for i in {0..16} ; do touch $i; done

At NFS client, no matter mounting through nfsv3 or nfsv4,
does ls (or ll) at the created test directory.

A tshark output likes following (for nfsv4),

# tshark -i eth0 tcp port 2049 -Tfields -e ip.src -e ip.dst -e nfs -e nfs.cookie4

srcip dstip SEQUENCE, PUTFH, READDIR 0
dstip srcip SEQUENCE PUTFH READDIR 909539109313539306,2108391201987888856,2305312124304486544,2566335452463141496,2978225129081509984,4263037479923412583,4304697173036510679,4666703455469210097,4759208201298769007,4776701232145978803,5338408478512081262,5949498658935544804,5971526429894832903,6294060338267709855,6528840566229532529,8600463293536422524,9223372036854775807
srcip dstip
srcip dstip SEQUENCE, PUTFH, READDIR 9223372036854775807
dstip srcip SEQUENCE PUTFH READDIR

The READDIR with cookie 9223372036854775807(0x7FFFFFFFFFFFFFFF) is redundant.

Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

show more ...

NFS: Convert kmap_atomic() to kmap_local_folio()

kmap_atomic() is deprecated in favor of kmap_local_{folio,page}().

Therefore, replace kmap_atomic() with kmap_local_folio() in
nfs_readdir_folio_arr

NFS: Convert kmap_atomic() to kmap_local_folio()

kmap_atomic() is deprecated in favor of kmap_local_{folio,page}().

Therefore, replace kmap_atomic() with kmap_local_folio() in
nfs_readdir_folio_array_append().

kmap_atomic() disables page-faults and preemption (the latter only for
!PREEMPT_RT kernels), However, the code within the mapping/un-mapping in
nfs_readdir_folio_array_append() does not depend on the above-mentioned
side effects.

Therefore, a mere replacement of the old API with the new one is all that
is required (i.e., there is no need to explicitly add any calls to
pagefault_disable() and/or preempt_disable()).

Tested with (x)fstests in a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel
with HIGHMEM64GB enabled.

Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Fixes: ec108d3cc766 ("NFS: Convert readdir page array functions to use a folio")
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

show more ...

nfs: fix another case of NULL/IS_ERR confusion wrt folio pointers

Dan has been improving on the smatch error pointer checks, and pointed
at another case where the __filemap_get_folio() conversion to

nfs: fix another case of NULL/IS_ERR confusion wrt folio pointers

Dan has been improving on the smatch error pointer checks, and pointed
at another case where the __filemap_get_folio() conversion to error
pointers had been overlooked. This time because it was hidden behind
the filemap_grab_folio() helper function that is a wrapper around it.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

nfs: fix mis-merged __filemap_get_folio() error check

Fix another case of an incorrect check for the returned 'folio' value
from __filemap_get_folio().

The failure case used to return NULL, but was

nfs: fix mis-merged __filemap_get_folio() error check

Fix another case of an incorrect check for the returned 'folio' value
from __filemap_get_folio().

The failure case used to return NULL, but was changed by commit
66dabbb65d67 ("mm: return an ERR_PTR from __filemap_get_folio").

But in the meantime, commit ec108d3cc766 ("NFS: Convert readdir page
array functions to use a folio") added a new user of that function.

And my merge of the two did not fix this up correctly.

The ext4 merge had the same issue, but that one had been caught in
linux-next and got properly fixed while merging.

Fixes: 0127f25b5dfc ("Merge tag 'nfs-for-6.4-1' of git://git.linux-nfs.org/projects/anna/linux-nfs")
Cc: Anna Schumaker <anna@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

NFS: Convert readdir page array functions to use a folio

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

NFS: Convert the readdir array-of-pages into an array-of-folios

This patch only converts the actual array, but doesn't touch the
individual nfs_cache_array pages and related functions (that will be

NFS: Convert the readdir array-of-pages into an array-of-folios

This patch only converts the actual array, but doesn't touch the
individual nfs_cache_array pages and related functions (that will be
done in the next patch).

I also adjust the names of the fields in the nfs_readdir_descriptor to
say "folio" instead of "page".

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

show more ...

NFS: Correct timing for assigning access cache timestamp

When the user's login time is newer than the cache's timestamp,
the original entry in the RB-tree will be replaced by a new entry.
Currently,

NFS: Correct timing for assigning access cache timestamp

When the user's login time is newer than the cache's timestamp,
the original entry in the RB-tree will be replaced by a new entry.
Currently, the timestamp is only set if the entry is not found in
the RB-tree, which can cause the timestamp to be undefined when
the entry exists. This may result in a significant increase in
ACCESS operations if the timestamp is set to zero.

Signed-off-by: Chengen Du <chengen.du@canonical.com>
Fixes: 0eb43812c027 ("NFS: Clear the file access cache upon login”)
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

show more ...

fs/nfs: Replace kmap_atomic() with kmap_local_page() in dir.c

kmap_atomic() is deprecated in favor of kmap_local_page().

With kmap_local_page() the mappings are per thread, CPU local, can take
page

fs/nfs: Replace kmap_atomic() with kmap_local_page() in dir.c

kmap_atomic() is deprecated in favor of kmap_local_page().

With kmap_local_page() the mappings are per thread, CPU local, can take
page-faults, and can be called from any context (including interrupts).
Furthermore, the tasks can be preempted and, when they are scheduled to
run again, the kernel virtual addresses are restored and still valid.

kmap_atomic() is implemented like a kmap_local_page() which also disables
page-faults and preemption (the latter only for !PREEMPT_RT kernels,
otherwise it only disables migration).

The code within the mappings/un-mappings in the functions of dir.c don't
depend on the above-mentioned side effects of kmap_atomic(), so that mere
replacements of the old API with the new one is all that is required
(i.e., there is no need to explicitly add calls to pagefault_disable()
and/or preempt_disable()).

Therefore, replace kmap_atomic() with kmap_local_page() in fs/nfs/dir.c.

Tested in a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel with
HIGHMEM64GB enabled.

Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

show more ...

fs: port ->permission() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is j

fs: port ->permission() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

show more ...

fs: port ->rename() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just

fs: port ->rename() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

show more ...

fs: port ->mknod() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just t

fs: port ->mknod() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

show more ...

fs: port ->mkdir() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just t

fs: port ->mkdir() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

show more ...

fs: port ->symlink() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just

fs: port ->symlink() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

show more ...

fs: port ->create() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just

fs: port ->create() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

show more ...

NFS: Fix up a sparse warning

sparse is warning about an incorrect RCU dereference.
fs/nfs/dir.c:2965:56: warning: incorrect type in argument 1 (different address spaces)
fs/nfs/dir.c:2965:56: exp

NFS: Fix up a sparse warning

sparse is warning about an incorrect RCU dereference.
fs/nfs/dir.c:2965:56: warning: incorrect type in argument 1 (different address spaces)
fs/nfs/dir.c:2965:56: expected struct cred const *
fs/nfs/dir.c:2965:56: got struct cred const [noderef] __rcu *const cred

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

show more ...

NFS: Judge the file access cache's timestamp in rcu path

If the user's login time is newer than the cache's timestamp,
we expect the cache may be stale and need to clear.
The stale cache will remain

NFS: Judge the file access cache's timestamp in rcu path

If the user's login time is newer than the cache's timestamp,
we expect the cache may be stale and need to clear.
The stale cache will remain in the list's tail if no other
users operate on that inode.
Once the user accesses the inode, the stale cache will be
returned in rcu path.

Signed-off-by: Chengen Du <chengen.du@canonical.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

show more ...

NFS: Trigger the "ls -l" readdir heuristic sooner

Since commit 1a34c8c9a49e ("NFS: Support larger readdir buffers") has
updated dtsize, and with recent improvements to the READDIRPLUS helper
heurist

NFS: Trigger the "ls -l" readdir heuristic sooner

Since commit 1a34c8c9a49e ("NFS: Support larger readdir buffers") has
updated dtsize, and with recent improvements to the READDIRPLUS helper
heuristic, the heuristic may not trigger until many dentries are emitted
to userspace. This will cause many thousands of GETATTR calls for "ls
-l" when the directory's pagecache has already been populated. This
manifests as poor performance for long directory listings after an
initially fast "ls -l".

Fix this by emitting only 17 entries for any first pass through the NFS
directory's ->iterate_shared(), which allows userpace to prime the
counters for the heuristic.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

show more ...

NFS: Clear the file access cache upon login

POSIX typically only refreshes the user's supplementary group
information upon login. Since NFS servers may often refresh their
concept of the user supple

NFS: Clear the file access cache upon login

POSIX typically only refreshes the user's supplementary group
information upon login. Since NFS servers may often refresh their
concept of the user supplementary group membership at their own cadence,
it is possible for the NFS client's access cache to become stale due to
the user's group membership changing on the server after the user has
already logged in on the client.
While it is reasonable to expect that such group membership changes are
rare, and that we do not want to optimise the cache to accommodate them,
it is also not unreasonable for the user to expect that if they log out
and log back in again, that the staleness would clear up.

Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Tested-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

show more ...

nfs: Remove redundant null checks before kfree

Fix the following coccicheck warning:
fs/nfs/dir.c:2494:2-7: WARNING:
NULL check before some freeing functions is not needed.

Signed-off-by: Yushan Zh

nfs: Remove redundant null checks before kfree

Fix the following coccicheck warning:
fs/nfs/dir.c:2494:2-7: WARNING:
NULL check before some freeing functions is not needed.

Signed-off-by: Yushan Zhou <katrinzhou@tencent.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

show more ...

nfs_finish_open(): don't open-code file_inode()

Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

NFS: unlink/rmdir shouldn't call d_delete() twice on ENOENT

nfs_unlink() calls d_delete() twice if it receives ENOENT from the
server - once in nfs_dentry_handle_enoent() from nfs_safe_remove and
on

NFS: unlink/rmdir shouldn't call d_delete() twice on ENOENT

nfs_unlink() calls d_delete() twice if it receives ENOENT from the
server - once in nfs_dentry_handle_enoent() from nfs_safe_remove and
once in nfs_dentry_remove_handle_error().

nfs_rmddir() also calls it twice - the nfs_dentry_handle_enoent() call
is direct and inside a region locked with ->rmdir_sem

It is safe to call d_delete() twice if the refcount > 1 as the dentry is
simply unhashed.
If the refcount is 1, the first call sets d_inode to NULL and the second
call crashes.

This patch guards the d_delete() call from nfs_dentry_handle_enoent()
leaving the one under ->remdir_sem in case that is important.

In mainline it would be safe to remove the d_delete() call. However in
older kernels to which this might be backported, that would change the
behaviour of nfs_unlink(). nfs_unlink() used to unhash the dentry which
resulted in nfs_dentry_handle_enoent() not calling d_delete(). So in
older kernels we need the d_delete() in nfs_dentry_remove_handle_error()
when called from nfs_unlink() but not when called from nfs_rmdir().

To make the code work correctly for old and new kernels, and from both
nfs_unlink() and nfs_rmdir(), we protect the d_delete() call with
simple_positive(). This ensures it is never called in a circumstance
where it could crash.

Fixes: 3c59366c207e ("NFS: don't unhash dentry during unlink/rename")
Fixes: 9019fb391de0 ("NFS: Label the dentry with a verifier in nfs_rmdir() and nfs_unlink()")
Signed-off-by: NeilBrown <neilb@suse.de>
Tested-by: Olga Kornievskaia <aglo@umich.edu>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

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NFS: Fix missing unlock in nfs_unlink()

Add the missing unlock before goto.

Fixes: 3c59366c207e ("NFS: don't unhash dentry during unlink/rename")
Signed-off-by: Sun Ke <sunke32@huawei.com>
Signed-o

NFS: Fix missing unlock in nfs_unlink()

Add the missing unlock before goto.

Fixes: 3c59366c207e ("NFS: don't unhash dentry during unlink/rename")
Signed-off-by: Sun Ke <sunke32@huawei.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

show more ...