* Possible data race on file->f_ra.ra_pages between generic_fadvise() and force_page_cache_readahead()
@ 2019-11-27 22:23 Meng Xu
0 siblings, 0 replies; only message in thread
From: Meng Xu @ 2019-11-27 22:23 UTC (permalink / raw)
To: linux-fsdevel
Hi VFS developers,
There might exists cases where file->f_ra.ra_pages may race in
generic_fadvise() and force_page_cache_readahead().
Following is the execution trace
[Setup]
create("file_bar", 511) = 3;
[Thread 1]
fadvise64(3, 9055, 975, 2);
ksys_fadvise64_64
vfs_fadvise
generic_fadvise
[WRITE] file->f_ra.ra_pages = bdi->ra_pages;
[Thread 2]
fadvise64(3, 9374, 3618, 3);
ksys_fadvise64_64
vfs_fadvise
generic_fadvise
force_page_cache_readahead
[READ] max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages);
I could confirm dynamically that the order between [READ] and [WRITE]
is not deterministic (i.e., either may go first). However, they do not
lead to any crash or panics so I guess this might not be a serious
issue.
But just in case there may be unintended consequences, I am posting
this issue here for more visibility. Feel free to comment and discuss.
Best Regards,
Meng
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2019-11-27 22:23 Possible data race on file->f_ra.ra_pages between generic_fadvise() and force_page_cache_readahead() Meng Xu
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