kernel/linux.git/fs/cachefiles/io.c, branch v6.19.11

cachefiles: Fix the incorrect return value in __cachefiles_write()

2025-07-10T07:40:17+00:00

In __cachefiles_write(), if the return value of the write operation > 0, it is set to 0. This makes it impossible to distinguish scenarios where a partial write has occurred, and will affect the outer calling functions: 1) cachefiles_write_complete() will call "term_func" such as netfs_write_subrequest_terminated(). When "ret" in __cachefiles_write() is used as the "transferred_or_error" of this function, it can not distinguish the amount of data written, makes the WARN meaningless. 2) cachefiles_ondemand_fd_write_iter() can only assume all writes were successful by default when "ret" is 0, and unconditionally return the full length specified by user space. Fix it by modifying "ret" to reflect the actual number of bytes written. Furthermore, returning a value greater than 0 from __cachefiles_write() does not affect other call paths, such as cachefiles_issue_write() and fscache_write(). Fixes: 047487c947e8 ("cachefiles: Implement the I/O routines") Signed-off-by: Zizhi Wo Link: https://lore.kernel.org/20250703024418.2809353-1-wozizhi@huaweicloud.com Signed-off-by: Christian Brauner

netfs: Fix the request's work item to not require a ref

2025-05-21T12:35:20+00:00

When the netfs_io_request struct's work item is queued, it must be supplied with a ref to the work item struct to prevent it being deallocated whilst on the queue or whilst it is being processed. This is tricky to manage as we have to get a ref before we try and queue it and then we may find it's already queued and is thus already holding a ref - in which case we have to try and get rid of the ref again. The problem comes if we're in BH or IRQ context and need to drop the ref: if netfs_put_request() reduces the count to 0, we have to do the cleanup - but the cleanup may need to wait. Fix this by adding a new work item to the request, ->cleanup_work, and dispatching that when the refcount hits zero. That can then synchronously cancel any outstanding work on the main work item before doing the cleanup. Adding a new work item also deals with another problem upstream where it's sometimes changing the work func in the put function and requeuing it - which has occasionally in the past caused the cleanup to happen incorrectly. As a bonus, this allows us to get rid of the 'was_async' parameter from a bunch of functions. This indicated whether the put function might not be permitted to sleep. Fixes: 3d3c95046742 ("netfs: Provide readahead and readpage netfs helpers") Signed-off-by: David Howells Link: https://lore.kernel.org/20250519090707.2848510-4-dhowells@redhat.com cc: Paulo Alcantara cc: Marc Dionne cc: Steve French cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

cachefiles: Add some subrequest tracepoints

2024-12-20T21:34:05+00:00

Add some tracepoints into the cachefiles write paths. Signed-off-by: David Howells Link: https://lore.kernel.org/r/20241216204124.3752367-16-dhowells@redhat.com cc: netfs@lists.linux.dev Signed-off-by: Christian Brauner

cachefiles, netfs: Fix write to partial block at EOF

2024-09-12T10:20:41+00:00

Because it uses DIO writes, cachefiles is unable to make a write to the backing file if that write is not aligned to and sized according to the backing file's DIO block alignment. This makes it tricky to handle a write to the cache where the EOF on the network file is not correctly aligned. To get around this, netfslib attempts to tell the driver it is calling how much more data there is available beyond the EOF that it can use to pad the write (netfslib preclears the part of the folio above the EOF). However, it tries to tell the cache what the maximum length is, but doesn't calculate this correctly; and, in any case, cachefiles actually ignores the value and just skips the block. Fix this by: (1) Change the value passed to indicate the amount of extra data that can be added to the operation (now ->submit_extendable_to). This is much simpler to calculate as it's just the end of the folio minus the top of the data within the folio - rather than having to account for data spread over multiple folios. (2) Make cachefiles add some of this data if the subrequest it is given ends at the network file's i_size if the extra data is sufficient to pad out to a whole block. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-22-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Move max_len/max_nr_segs from netfs_io_subrequest to netfs_io_stream

2024-09-05T09:00:41+00:00

Move max_len/max_nr_segs from struct netfs_io_subrequest to struct netfs_io_stream as we only issue one subreq at a time and then don't need these values again for that subreq unless and until we have to retry it - in which case we want to renegotiate them. Signed-off-by: David Howells cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20240814203850.2240469-8-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

cachefiles: Set the max subreq size for cache writes to MAX_RW_COUNT

2024-07-24T08:53:13+00:00

Set the maximum size of a subrequest that writes to cachefiles to be MAX_RW_COUNT so that we don't overrun the maximum write we can make to the backing filesystem. Signed-off-by: David Howells Link: https://lore.kernel.org/r/1599005.1721398742@warthog.procyon.org.uk cc: Jeff Layton cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner

netfs, cachefiles: Implement helpers for new write code

2024-05-01T17:07:37+00:00

Implement the helpers for the new write code in cachefiles. There's now an optional ->prepare_write() that allows the filesystem to set the parameters for the next write, such as maximum size and maximum segment count, and an ->issue_write() that is called to initiate an (asynchronous) write operation. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: netfs@lists.linux.dev cc: linux-erofs@lists.ozlabs.org cc: linux-fsdevel@vger.kernel.org

netfs: Switch to using unsigned long long rather than loff_t

2024-05-01T17:07:35+00:00

Switch to using unsigned long long rather than loff_t in netfslib to avoid problems with the sign flipping in the maths when we're dealing with the byte at position 0x7fffffffffffffff. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: Ilya Dryomov cc: Xiubo Li cc: netfs@lists.linux.dev cc: ceph-devel@vger.kernel.org cc: linux-fsdevel@vger.kernel.org

Merge tag 'vfs-6.8.netfs' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs

2024-01-19T17:10:23+00:00

Pull netfs updates from Christian Brauner: "This extends the netfs helper library that network filesystems can use to replace their own implementations. Both afs and 9p are ported. cifs is ready as well but the patches are way bigger and will be routed separately once this is merged. That will remove lots of code as well. The overal goal is to get high-level I/O and knowledge of the page cache and ouf of the filesystem drivers. This includes knowledge about the existence of pages and folios The pull request converts afs and 9p. This removes about 800 lines of code from afs and 300 from 9p. For 9p it is now possible to do writes in larger than a page chunks. Additionally, multipage folio support can be turned on for 9p. Separate patches exist for cifs removing another 2000+ lines. I've included detailed information in the individual pulls I took. Summary: - Add NFS-style (and Ceph-style) locking around DIO vs buffered I/O calls to prevent these from happening at the same time. - Support for direct and unbuffered I/O. - Support for write-through caching in the page cache. - O_*SYNC and RWF_*SYNC writes use write-through rather than writing to the page cache and then flushing afterwards. - Support for write-streaming. - Support for write grouping. - Skip reads for which the server could only return zeros or EOF. - The fscache module is now part of the netfs library and the corresponding maintainer entry is updated. - Some helpers from the fscache subsystem are renamed to mark them as belonging to the netfs library. - Follow-up fixes for the netfs library. - Follow-up fixes for the 9p conversion" * tag 'vfs-6.8.netfs' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (50 commits) netfs: Fix wrong #ifdef hiding wait cachefiles: Fix signed/unsigned mixup netfs: Fix the loop that unmarks folios after writing to the cache netfs: Fix interaction between write-streaming and cachefiles culling netfs: Count DIO writes netfs: Mark netfs_unbuffered_write_iter_locked() static netfs: Fix proc/fs/fscache symlink to point to "netfs" not "../netfs" netfs: Rearrange netfs_io_subrequest to put request pointer first 9p: Use length of data written to the server in preference to error 9p: Do a couple of cleanups 9p: Fix initialisation of netfs_inode for 9p cachefiles: Fix __cachefiles_prepare_write() 9p: Use netfslib read/write_iter afs: Use the netfs write helpers netfs: Export the netfs_sreq tracepoint netfs: Optimise away reads above the point at which there can be no data netfs: Implement a write-through caching option netfs: Provide a launder_folio implementation netfs: Provide a writepages implementation netfs, cachefiles: Pass upper bound length to allow expansion ...

cachefiles: Fix signed/unsigned mixup

2024-01-09T13:32:44+00:00

In __cachefiles_prepare_write(), the start and pos variables were made unsigned 64-bit so that the casts in the checking could be got rid of - which should be fine since absolute file offsets can't be negative, except that an error code may be obtained from vfs_llseek(), which *would* be negative. This breaks the error check. Fix this for now by reverting pos and start to be signed and putting back the casts. Unfortunately, the error value checks cannot be replaced with IS_ERR_VALUE() as long might be 32-bits. Fixes: 7097c96411d2 ("cachefiles: Fix __cachefiles_prepare_write()") Reported-by: Simon Horman Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202401071152.DbKqMQMu-lkp@intel.com/ Signed-off-by: David Howells Reviewed-by: Simon Horman Reviewed-by: Gao Xiang cc: Yiqun Leng cc: Jia Zhu cc: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-erofs@lists.ozlabs.org cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org