Yafang Shao 0a2d82946b mm: allow read-ahead with IOCB_NOWAIT set ... Readahead support for IOCB_NOWAIT was introduced in commit 2e85abf053 ("mm: allow read-ahead with IOCB_NOWAIT set"). However, this implementation broke the semantics of IOCB_NOWAIT by potentially causing it to wait on I/O during memory reclamation. This behavior was later modified in commit efa8480a83 ("fs: RWF_NOWAIT should imply IOCB_NOIO"). To resolve the blocking issue during memory reclamation, we can use memalloc_noio_{save,restore} to ensure non-blocking behavior. This change restores the original functionality, allowing preadv2(IOCB_NOWAIT) to trigger readahead if the file content is not present in the page cache. While this process may trigger direct memory reclamation, the __GFP_NORETRY flag is set in the readahead GFP flags, ensuring it won't block. A use case for this change is when we want to trigger readahead in the preadv2(2) syscall if the file cache is absent, but without waiting for certain filesystem locks, like xfs_ilock. A simple example is as follows: retry: if (preadv2(fd, iovec, cnt, offset, RWF_NOWAIT) < 0) { do_other_work(); goto retry; } Link: https://lore.gnuweeb.org/io-uring/20200624164127.GP21350@casper.infradead.org/ Link: https://lkml.kernel.org/r/20240820022639.89562-1-laoar.shao@gmail.com Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Matthew Wilcox <willy@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>		2024-09-03 21:15:40 -07:00
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acpi	ACPI: video: Add Dell UART backlight controller detection	2024-08-19 15:58:35 +02:00
asm-generic	arch_numa: switch over to numa_memblks	2024-09-03 21:15:32 -07:00
clocksource	…
crypto	…
drm	A revert for a previous TTM commit causing stuttering, 3 fixes for	2024-08-30 11:28:11 +10:00
dt-bindings	I3C for 6.11	2024-07-27 10:53:06 -07:00
keys	…
kunit	…
kvm	…
linux	mm: allow read-ahead with IOCB_NOWAIT set	2024-09-03 21:15:40 -07:00
math-emu	…
media	…
memory	…
misc	…
net	netfilter pull request 24-08-28	2024-08-29 11:35:54 +02:00
pcmcia	…
ras	…
rdma	…
rv	…
scsi	scsi: core: Fix the return value of scsi_logical_block_count()	2024-08-16 21:02:06 -04:00
soc	net: mscc: ocelot: treat 802.1ad tagged traffic as 802.1Q-untagged	2024-08-16 09:59:32 +01:00
sound	ASoC: Fixes for v6.11	2024-08-09 09:58:07 +02:00
target	…
trace	filemap: add trace events for get_pages, map_pages, and fault	2024-09-01 20:26:10 -07:00
uapi	mm: remove PG_error	2024-09-01 20:26:05 -07:00
ufs	scsi: ufs: core: Add a quirk for handling broken LSDBS field in controller capabilities register	2024-08-16 21:09:17 -04:00
vdso	…
video	…
xen	…