kernel/linux.git/fs/netfs/iterator.c, branch v6.12.80

netfs: Fix kernel BUG in netfs_limit_iter() for ITER_KVEC iterators

2026-04-02T11:09:52+00:00

[ Upstream commit 67e467a11f62ff64ad219dc6aa5459e132c79d14 ] When a process crashes and the kernel writes a core dump to a 9P filesystem, __kernel_write() creates an ITER_KVEC iterator. This iterator reaches netfs_limit_iter() via netfs_unbuffered_write(), which only handles ITER_FOLIOQ, ITER_BVEC and ITER_XARRAY iterator types, hitting the BUG() for any other type. Fix this by adding netfs_limit_kvec() following the same pattern as netfs_limit_bvec(), since both kvec and bvec are simple segment arrays with pointer and length fields. Dispatch it from netfs_limit_iter() when the iterator type is ITER_KVEC. Fixes: cae932d3aee5 ("netfs: Add func to calculate pagecount/size-limited span of an iterator") Reported-by: syzbot+9c058f0d63475adc97fd@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9c058f0d63475adc97fd Tested-by: syzbot+9c058f0d63475adc97fd@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey Link: https://patch.msgid.link/20260307090041.359870-1-kartikey406@gmail.com Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

netfs: Speed up buffered reading

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

Improve the efficiency of buffered reads in a number of ways: (1) Overhaul the algorithm in general so that it's a lot more compact and split the read submission code between buffered and unbuffered versions. The unbuffered version can be vastly simplified. (2) Read-result collection is handed off to a work queue rather than being done in the I/O thread. Multiple subrequests can be processes simultaneously. (3) When a subrequest is collected, any folios it fully spans are collected and "spare" data on either side is donated to either the previous or the next subrequest in the sequence. Notes: (*) Readahead expansion is massively slows down fio, presumably because it causes a load of extra allocations, both folio and xarray, up front before RPC requests can be transmitted. (*) RDMA with cifs does appear to work, both with SIW and RXE. (*) PG_private_2-based reading and copy-to-cache is split out into its own file and altered to use folio_queue. Note that the copy to the cache now creates a new write transaction against the cache and adds the folios to be copied into it. This allows it to use part of the writeback I/O code. 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/20240814203850.2240469-20-dhowells@redhat.com/ # v2 Signed-off-by: Christian Brauner

netfs: Add func to calculate pagecount/size-limited span of an iterator

2023-12-28T09:45:18+00:00

Add a function to work out how much of an ITER_BVEC or ITER_XARRAY iterator we can use in a pagecount-limited and size-limited span. This will be used, for example, to limit the number of segments in a subrequest to the maximum number of elements that an RDMA transfer can handle. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org

Move netfs_extract_iter_to_sg() to lib/scatterlist.c

2023-06-08T11:42:33+00:00

Move netfs_extract_iter_to_sg() to lib/scatterlist.c as it's going to be used by more than just network filesystems (AF_ALG, for example). Signed-off-by: David Howells cc: Jeff Layton cc: Steve French cc: Shyam Prasad N cc: Rohith Surabattula cc: Jens Axboe cc: Herbert Xu cc: "David S. Miller" cc: Eric Dumazet cc: Jakub Kicinski cc: Paolo Abeni cc: Matthew Wilcox cc: linux-crypto@vger.kernel.org cc: linux-cachefs@redhat.com cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: netdev@vger.kernel.org Signed-off-by: Paolo Abeni

Wrap lines at 80

2023-06-08T11:42:33+00:00

Wrap a line at 80 to stop checkpatch complaining. Signed-off-by: David Howells cc: Jeff Layton cc: Steve French cc: Shyam Prasad N cc: Rohith Surabattula cc: Jens Axboe cc: Herbert Xu cc: "David S. Miller" cc: Eric Dumazet cc: Jakub Kicinski cc: Paolo Abeni cc: Matthew Wilcox cc: Simon Horman cc: linux-crypto@vger.kernel.org cc: linux-cachefs@redhat.com cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: netdev@vger.kernel.org Signed-off-by: Paolo Abeni

Fix a couple of spelling mistakes

2023-06-08T11:42:33+00:00

Fix a couple of spelling mistakes in a comment. Suggested-by: Simon Horman Link: https://lore.kernel.org/r/ZHH2mSRqeL4Gs1ft@corigine.com/ Link: https://lore.kernel.org/r/ZHH1nqZWOGzxlidT@corigine.com/ Signed-off-by: David Howells Reviewed-by: Simon Horman cc: Jeff Layton cc: Steve French cc: Shyam Prasad N cc: Rohith Surabattula cc: Jens Axboe cc: Herbert Xu cc: "David S. Miller" cc: Eric Dumazet cc: Jakub Kicinski cc: Paolo Abeni cc: Matthew Wilcox cc: linux-crypto@vger.kernel.org cc: linux-cachefs@redhat.com cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: netdev@vger.kernel.org Signed-off-by: Paolo Abeni

Drop the netfs_ prefix from netfs_extract_iter_to_sg()

2023-06-08T11:42:33+00:00

Rename netfs_extract_iter_to_sg() and its auxiliary functions to drop the netfs_ prefix. Signed-off-by: David Howells cc: Jeff Layton cc: Steve French cc: Shyam Prasad N cc: Rohith Surabattula cc: Jens Axboe cc: Herbert Xu cc: "Matthew Wilcox (Oracle)" cc: "David S. Miller" cc: Eric Dumazet cc: Jakub Kicinski cc: Paolo Abeni cc: linux-crypto@vger.kernel.org cc: linux-cachefs@redhat.com cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: netdev@vger.kernel.org Signed-off-by: Paolo Abeni

netfs: Fix netfs_extract_iter_to_sg() for ITER_UBUF/IOVEC

2023-04-12T16:26:36+00:00

Fix netfs_extract_iter_to_sg() for ITER_UBUF and ITER_IOVEC to set the size of the page to the part of the page extracted, not the remaining amount of data in the extracted page array at that point. This doesn't yet affect anything as cifs, the only current user, only passes in non-user-backed iterators. Fixes: 018584697533 ("netfs: Add a function to extract an iterator into a scatterlist") Signed-off-by: David Howells Reviewed-by: Jeff Layton Cc: Steve French Cc: Shyam Prasad N Cc: Rohith Surabattula Signed-off-by: Linus Torvalds

iov: Fix netfs_extract_user_to_sg()

2023-03-02T00:18:25+00:00

Fix the loop check in netfs_extract_user_to_sg() for extraction from user-backed iterators to do the body if npages > 0, not if npages < 0 (which it can never be). This isn't currently used by cifs, which only ever extracts data from BVEC, KVEC and XARRAY iterators at this level, user-backed iterators having being decanted into BVEC iterators at a higher level to accommodate the work being done in a kernel thread. Found by smatch: fs/netfs/iterator.c:139 netfs_extract_user_to_sg() warn: unsigned 'npages' is never less than zero. Fixes: 018584697533 ("netfs: Add a function to extract an iterator into a scatterlist") Reported-by: kernel test robot Link: https://lore.kernel.org/oe-kbuild-all/202302261115.P3TQi1ZO-lkp@intel.com/ Reported-by: Dan Carpenter Link: https://lore.kernel.org/r/Y/yYnAhoAYDBKixX@kili Reviewed-by: Paulo Alcantara (SUSE) Signed-off-by: David Howells cc: Jeff Layton cc: linux-cifs@vger.kernel.org cc: linux-cachefs@redhat.com Signed-off-by: Steve French

Merge tag '6.3-rc-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6

2023-02-23T01:12:44+00:00

Pull cifs client updates from Steve French: "The largest subset of this is from David Howells et al: making the cifs/smb3 driver pass iov_iters down to the lowest layers, directly to the network transport rather than passing lists of pages around, helping multiple areas: - Pin user pages, thereby fixing the race between concurrent DIO read and fork, where the pages containing the DIO read buffer may end up belonging to the child process and not the parent - with the result that the parent might not see the retrieved data. - cifs shouldn't take refs on pages extracted from non-user-backed iterators (eg. KVEC). With these changes, cifs will apply the appropriate cleanup. - Making it easier to transition to using folios in cifs rather than pages by dealing with them through BVEC and XARRAY iterators. - Allowing cifs to use the new splice function The remainder are: - fixes for stable, including various fixes for uninitialized memory, wrong length field causing mount issue to very old servers, important directory lease fixes and reconnect fixes - cleanups (unused code removal, change one element array usage, and a change form strtobool to kstrtobool, and Kconfig cleanups) - SMBDIRECT (RDMA) fixes including iov_iter integration and UAF fixes - reconnect fixes - multichannel fixes, including improving channel allocation (to least used channel) - remove the last use of lock_page_killable by moving to folio_lock_killable" * tag '6.3-rc-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6: (46 commits) update internal module version number for cifs.ko cifs: update ip_addr for ses only for primary chan setup cifs: use tcon allocation functions even for dummy tcon cifs: use the least loaded channel for sending requests cifs: DIO to/from KVEC-type iterators should now work cifs: Remove unused code cifs: Build the RDMA SGE list directly from an iterator cifs: Change the I/O paths to use an iterator rather than a page list cifs: Add a function to read into an iter from a socket cifs: Add some helper functions cifs: Add a function to Hash the contents of an iterator cifs: Add a function to build an RDMA SGE list from an iterator netfs: Add a function to extract an iterator into a scatterlist netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator cifs: Implement splice_read to pass down ITER_BVEC not ITER_PIPE splice: Export filemap/direct_splice_read() iov_iter: Add a function to extract a page list from an iterator iov_iter: Define flags to qualify page extraction. splice: Add a func to do a splice from an O_DIRECT file without ITER_PIPE splice: Add a func to do a splice from a buffered file without ITER_PIPE ...