kernel/linux.git/mm/readahead.c, branch v5.15.208

vfs: fix readahead(2) on block devices

2023-11-20T10:08:13+00:00

[ Upstream commit 7116c0af4b8414b2f19fdb366eea213cbd9d91c2 ] Readahead was factored to call generic_fadvise. That refactor added an S_ISREG restriction which broke readahead on block devices. In addition to S_ISREG, this change checks S_ISBLK to fix block device readahead. There is no change in behavior with any file type besides block devices in this change. Fixes: 3d8f7615319b ("vfs: implement readahead(2) using POSIX_FADV_WILLNEED") Signed-off-by: Reuben Hawkins Link: https://lore.kernel.org/r/20231003015704.2415-1-reubenhwk@gmail.com Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

mm: Protect operations adding pages to page cache with invalidate_lock

2021-07-13T11:14:27+00:00

Currently, serializing operations such as page fault, read, or readahead against hole punching is rather difficult. The basic race scheme is like: fallocate(FALLOC_FL_PUNCH_HOLE) read / fault / .. truncate_inode_pages_range() Now the problem is in this way read / page fault / readahead can instantiate pages in page cache with potentially stale data (if blocks get quickly reused). Avoiding this race is not simple - page locks do not work because we want to make sure there are *no* pages in given range. inode->i_rwsem does not work because page fault happens under mmap_sem which ranks below inode->i_rwsem. Also using it for reads makes the performance for mixed read-write workloads suffer. So create a new rw_semaphore in the address_space - invalidate_lock - that protects adding of pages to page cache for page faults / reads / readahead. Reviewed-by: Darrick J. Wong Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara

mm: Implement readahead_control pageset expansion

2021-04-23T09:14:29+00:00

Provide a function, readahead_expand(), that expands the set of pages specified by a readahead_control object to encompass a revised area with a proposed size and length. The proposed area must include all of the old area and may be expanded yet more by this function so that the edges align on (transparent huge) page boundaries as allocated. The expansion will be cut short if a page already exists in either of the areas being expanded into. Note that any expansion made in such a case is not rolled back. This will be used by fscache so that reads can be expanded to cache granule boundaries, thereby allowing whole granules to be stored in the cache, but there are other potential users also. Changes: v6: - Fold in a patch from Matthew Wilcox to tell the ondemand readahead algorithm about the expansion so that the next readahead starts at the right place[2]. v4: - Moved the declaration of readahead_expand() to a better place[1]. Suggested-by: Matthew Wilcox (Oracle) Signed-off-by: David Howells Reviewed-by: Matthew Wilcox (Oracle) Tested-by: Jeff Layton Tested-by: Dave Wysochanski Tested-By: Marc Dionne cc: Alexander Viro cc: Christoph Hellwig cc: Mike Marshall cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20210217161358.GM2858050@casper.infradead.org/ [1] Link: https://lore.kernel.org/r/20210407201857.3582797-4-willy@infradead.org/ [2] Link: https://lore.kernel.org/r/159974633888.2094769.8326206446358128373.stgit@warthog.procyon.org.uk/ Link: https://lore.kernel.org/r/160588479816.3465195.553952688795241765.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161118131787.1232039.4863969952441067985.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/161161028670.2537118.13831420617039766044.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161340389201.1303470.14353807284546854878.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/161539530488.286939.18085961677838089157.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/161653789422.2770958.2108046612147345000.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/161789069829.6155.4295672417565512161.stgit@warthog.procyon.org.uk/ # v6

mm/readahead: Handle ractl nr_pages being modified

2021-04-23T09:14:28+00:00

Filesystems are not currently permitted to modify the number of pages in the ractl. An upcoming patch to add readahead_expand() changes that rule, so remove the check and resync the loop counter after every call to the filesystem. Tested-by: Jeff Layton Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: David Howells Link: https://lore.kernel.org/r/20210420200116.3715790-1-willy@infradead.org/ Link: https://lore.kernel.org/r/20210421170923.4005574-1-willy@infradead.org/ # v2

mm/filemap: Pass the file_ra_state in the ractl

2021-04-23T08:25:00+00:00

For readahead_expand(), we need to modify the file ra_state, so pass it down by adding it to the ractl. We have to do this because it's not always the same as f_ra in the struct file that is already being passed. Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: David Howells Tested-by: Jeff Layton Tested-by: Dave Wysochanski Tested-By: Marc Dionne Link: https://lore.kernel.org/r/20210407201857.3582797-2-willy@infradead.org/ Link: https://lore.kernel.org/r/161789067431.6155.8063840447229665720.stgit@warthog.procyon.org.uk/ # v6

mm: use limited read-ahead to satisfy read

2020-10-17T19:49:08+00:00

For the case where read-ahead is disabled on the file, or if the cgroup is congested, ensure that we can at least do 1 page of read-ahead to make progress on the read in an async fashion. This could potentially be larger, but it's not needed in terms of functionality, so let's error on the side of caution as larger counts of pages may run into reclaim issues (particularly if we're congested). This makes sure we're not hitting the potentially sync ->readpage() path for IO that is marked IOCB_WAITQ, which could cause us to block. It also means we'll use the same path for IO, regardless of whether or not read-ahead happens to be disabled on the lower level device. Acked-by: Johannes Weiner Reported-by: Matthew Wilcox (Oracle) Reported-by: Hao_Xu [axboe: updated for new ractl API] Signed-off-by: Jens Axboe

mm/readahead: pass a file_ra_state into force_page_cache_ra

2020-10-16T18:11:16+00:00

The file_ra_state being passed into page_cache_sync_readahead() was being ignored in favour of using the one embedded in the struct file. The only caller for which this makes a difference is the fsverity code if the file has been marked as POSIX_FADV_RANDOM, but it's confusing and worth fixing. Signed-off-by: David Howells Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton Cc: Eric Biggers Link: https://lkml.kernel.org/r/20200903140844.14194-10-willy@infradead.org Signed-off-by: Linus Torvalds

mm/readahead: add page_cache_sync_ra and page_cache_async_ra

2020-10-16T18:11:16+00:00

Reimplement page_cache_sync_readahead() and page_cache_async_readahead() as wrappers around versions of the function which take a readahead_control in preparation for making do_sync_mmap_readahead() pass down an RAC struct. Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton Cc: David Howells Cc: Eric Biggers Link: https://lkml.kernel.org/r/20200903140844.14194-8-willy@infradead.org Signed-off-by: Linus Torvalds

mm/readahead: pass readahead_control to force_page_cache_ra

2020-10-16T18:11:16+00:00

Reimplement force_page_cache_readahead() as a wrapper around force_page_cache_ra(). Pass the existing readahead_control from page_cache_sync_readahead(). Signed-off-by: David Howells Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton Cc: Eric Biggers Link: https://lkml.kernel.org/r/20200903140844.14194-7-willy@infradead.org Signed-off-by: Linus Torvalds

mm/readahead: make ondemand_readahead take a readahead_control

2020-10-16T18:11:16+00:00

Make ondemand_readahead() take a readahead_control struct in preparation for making do_sync_mmap_readahead() pass down an RAC struct. Signed-off-by: David Howells Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton Cc: Eric Biggers Link: https://lkml.kernel.org/r/20200903140844.14194-6-willy@infradead.org Signed-off-by: Linus Torvalds