kernel/Documentation/filesystems/porting, branch linux-5.1.y

dcache: sort the freeing-without-RCU-delay mess for good.

2019-05-25T16:16:24Z

commit 5467a68cbf6884c9a9d91e2a89140afb1839c835 upstream. For lockless accesses to dentries we don't have pinned we rely (among other things) upon having an RCU delay between dropping the last reference and actually freeing the memory. On the other hand, for things like pipes and sockets we neither do that kind of lockless access, nor want to deal with the overhead of an RCU delay every time a socket gets closed. So delay was made optional - setting DCACHE_RCUACCESS in ->d_flags made sure it would happen. We tried to avoid setting it unless we knew we need it. Unfortunately, that had led to recurring class of bugs, in which we missed the need to set it. We only really need it for dentries that are created by d_alloc_pseudo(), so let's not bother with trying to be smart - just make having an RCU delay the default. The ones that do *not* get it set the replacement flag (DCACHE_NORCU) and we'd better use that sparingly. d_alloc_pseudo() is the only such user right now. FWIW, the race that finally prompted that switch had been between __lock_parent() of immediate subdirectory of what's currently the root of a disconnected tree (e.g. from open-by-handle in progress) racing with d_splice_alias() elsewhere picking another alias for the same inode, either on outright corrupted fs image, or (in case of open-by-handle on NFS) that subdirectory having been just moved on server. It's not easy to hit, so the sky is not falling, but that's not the first race on similar missed cases and the logics for settinf DCACHE_RCUACCESS has gotten ridiculously convoluted. Cc: stable@vger.kernel.org Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

Merge tag 'xfs-4.20-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

2018-11-02T16:33:08Z

Pull vfs dedup fixes from Dave Chinner: "This reworks the vfs data cloning infrastructure. We discovered many issues with these interfaces late in the 4.19 cycle - the worst of them (data corruption, setuid stripping) were fixed for XFS in 4.19-rc8, but a larger rework of the infrastructure fixing all the problems was needed. That rework is the contents of this pull request. Rework the vfs_clone_file_range and vfs_dedupe_file_range infrastructure to use a common .remap_file_range method and supply generic bounds and sanity checking functions that are shared with the data write path. The current VFS infrastructure has problems with rlimit, LFS file sizes, file time stamps, maximum filesystem file sizes, stripping setuid bits, etc and so they are addressed in these commits. We also introduce the ability for the ->remap_file_range methods to return short clones so that clones for vfs_copy_file_range() don't get rejected if the entire range can't be cloned. It also allows filesystems to sliently skip deduplication of partial EOF blocks if they are not capable of doing so without requiring errors to be thrown to userspace. Existing filesystems are converted to user the new remap_file_range method, and both XFS and ocfs2 are modified to make use of the new generic checking infrastructure" * tag 'xfs-4.20-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: (28 commits) xfs: remove [cm]time update from reflink calls xfs: remove xfs_reflink_remap_range xfs: remove redundant remap partial EOF block checks xfs: support returning partial reflink results xfs: clean up xfs_reflink_remap_blocks call site xfs: fix pagecache truncation prior to reflink ocfs2: remove ocfs2_reflink_remap_range ocfs2: support partial clone range and dedupe range ocfs2: fix pagecache truncation prior to reflink ocfs2: truncate page cache for clone destination file before remapping vfs: clean up generic_remap_file_range_prep return value vfs: hide file range comparison function vfs: enable remap callers that can handle short operations vfs: plumb remap flags through the vfs dedupe functions vfs: plumb remap flags through the vfs clone functions vfs: make remap_file_range functions take and return bytes completed vfs: remap helper should update destination inode metadata vfs: pass remap flags to generic_remap_checks vfs: pass remap flags to generic_remap_file_range_prep vfs: combine the clone and dedupe into a single remap_file_range ...

vfs: combine the clone and dedupe into a single remap_file_range

2018-10-29T23:41:21Z

Combine the clone_file_range and dedupe_file_range operations into a single remap_file_range file operation dispatch since they're fundamentally the same operation. The differences between the two can be made in the prep functions. Signed-off-by: Darrick J. Wong Reviewed-by: Amir Goldstein Reviewed-by: Christoph Hellwig Signed-off-by: Dave Chinner

Document d_splice_alias() calling conventions for ->lookup() users.

2018-10-10T20:52:37Z

Short version: it does the right thing when given NULL or ERR_PTR(...) and its calling conventions are chosen to have minimal PITA when used in ->lookup() instances. Signed-off-by: Al Viro

document alloc_file() changes

2018-07-12T14:04:29Z

Acked-by: Linus Torvalds Signed-off-by: Al Viro

document ->atomic_open() changes

2018-07-12T14:04:22Z

Acked-by: Linus Torvalds Signed-off-by: Al Viro

vfs: grab the lock instead of blocking in __fd_install during resizing

2017-11-05T23:58:07Z

Explicit locking in the fallback case provides a safe state of the table. Getting rid of blocking semantics makes __fd_install usable again in non-sleepable contexts, which easies backporting efforts. There is a side effect of slightly nicer assembly for the common case as might_sleep can now be removed. Signed-off-by: Mateusz Guzik Signed-off-by: Al Viro

VFS: Differentiate mount flags (MS_*) from internal superblock flags

2017-07-17T07:45:35Z

Differentiate the MS_* flags passed to mount(2) from the internal flags set in the super_block's s_flags. s_flags are now called SB_*, with the names and the values for the moment mirroring the MS_* flags that they're equivalent to. In this patch, just the headers are altered and some kernel code where blind automated conversion isn't necessarily correct. Note that this shows up some interesting issues: (1) Some MS_* flags get translated to MNT_* flags (such as MS_NODEV -> MNT_NODEV) without passing this on to the filesystem, but some filesystems set such flags anyway. (2) The ->remount_fs() methods of some filesystems adjust the *flags argument by setting MS_* flags in it, such as MS_NOATIME - but these flags are then scrubbed by do_remount_sb() (only the occupants of MS_RMT_MASK are permitted: MS_RDONLY, MS_SYNCHRONOUS, MS_MANDLOCK, MS_I_VERSION and MS_LAZYTIME) I'm not sure what's the best way to solve all these cases. Suggested-by: Al Viro Signed-off-by: David Howells

Documentation/filesystems: fix documentation for ->getattr()

2017-04-03T05:05:56Z

Following the recent merge of statx, correct the documented prototype for the ->getattr() inode operation, and add an entry to the porting file. Signed-off-by: Eric Biggers Signed-off-by: David Howells Signed-off-by: Al Viro

vfs: default to generic_readlink()

2016-12-09T15:45:04Z

If i_op->readlink is NULL, but i_op->get_link is set then vfs_readlink() defaults to calling generic_readlink(). The IOP_DEFAULT_READLINK flag indicates that the above conditions are met and the default action can be taken. Signed-off-by: Miklos Szeredi