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| author | Andrew Morton | 2006-08-05 21:14:25 +0200 |
|---|---|---|
| committer | Linus Torvalds | 2006-08-06 17:57:47 +0200 |
| commit | 60c371bc753495f36d3a71338b46030f7fffce3b (patch) | |
| tree | ec83d5b3cc89efcea66310f3a1c6ca3708f6a26e /mm | |
| parent | [PATCH] au1100fb: Fix startup sequence (diff) | |
| download | kernel-qcow2-linux-60c371bc753495f36d3a71338b46030f7fffce3b.tar.gz kernel-qcow2-linux-60c371bc753495f36d3a71338b46030f7fffce3b.tar.xz kernel-qcow2-linux-60c371bc753495f36d3a71338b46030f7fffce3b.zip | |
[PATCH] fadvise() make POSIX_FADV_NOREUSE a no-op
The POSIX_FADV_NOREUSE hint means "the application will use this range of the
file a single time". It seems to be intended that the implementation will use
this hint to perform drop-behind of that part of the file when the application
gets around to reading or writing it.
However for reasons which aren't obvious (or sane?) I mapped
POSIX_FADV_NOREUSE onto POSIX_FADV_WILLNEED. ie: it does readahead.
That's daft. So for now, make POSIX_FADV_NOREUSE a no-op.
This is a non-back-compatible change. If someone was using POSIX_FADV_NOREUSE
to perform readahead, they lose. The likelihood is low.
If/when we later implement POSIX_FADV_NOREUSE things will get interesting - to
do it fully we'll need to maintain file offset/length ranges and peform all
sorts of complex tricks, and managing the lifetime of those ranges' data
structures will be interesting..
A sensible implementation would probably ignore the file range and would
simply mark the entire file as needing some form of drop-behind treatment.
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/fadvise.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/fadvise.c b/mm/fadvise.c index 60a5d55e51d9..168c78a121bb 100644 --- a/mm/fadvise.c +++ b/mm/fadvise.c @@ -73,7 +73,6 @@ asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) file->f_ra.ra_pages = bdi->ra_pages * 2; break; case POSIX_FADV_WILLNEED: - case POSIX_FADV_NOREUSE: if (!mapping->a_ops->readpage) { ret = -EINVAL; break; @@ -94,6 +93,8 @@ asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice) if (ret > 0) ret = 0; break; + case POSIX_FADV_NOREUSE: + break; case POSIX_FADV_DONTNEED: if (!bdi_write_congested(mapping->backing_dev_info)) filemap_flush(mapping); |