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author | Al Viro <viro@zeniv.linux.org.uk> | 2020-03-12 21:07:27 +0300 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2020-04-02 08:09:31 +0300 |
commit | 99a4a90c8e9337e364136393286544e3753673c3 (patch) | |
tree | fa8da0e7badc7334154f0d5b400bf604cf1dac25 /fs/internal.h | |
parent | d489cf9a3e88aafc6c9f55c36ff7bbca2c25d54a (diff) | |
download | linux-99a4a90c8e9337e364136393286544e3753673c3.tar.xz |
lookup_open(): don't bother with fallbacks to lookup+create
We fall back to lookup+create (instead of atomic_open) in several cases:
1) we don't have write access to filesystem and O_TRUNC is
present in the flags. It's not something we want ->atomic_open() to
see - it just might go ahead and truncate the file. However, we can
pass it the flags sans O_TRUNC - eventually do_open() will call
handle_truncate() anyway.
2) we have O_CREAT | O_EXCL and we can't write to parent.
That's going to be an error, of course, but we want to know _which_
error should that be - might be EEXIST (if file exists), might be
EACCES or EROFS. Simply stripping O_CREAT (and checking if we see
ENOENT) would suffice, if not for O_EXCL. However, we used to have
->atomic_open() fully responsible for rejecting O_CREAT | O_EXCL
on existing file and just stripping O_CREAT would've disarmed
those checks. With nothing downstream to catch the problem -
FMODE_OPENED used to be "don't bother with EEXIST checks,
->atomic_open() has done those". Now EEXIST checks downstream
are skipped only if FMODE_CREATED is set - FMODE_OPENED alone
is not enough. That has eliminated the need to fall back onto
lookup+create path in this case.
3) O_WRONLY or O_RDWR when we have no write access to
filesystem, with nothing else objectionable. Fallback is
(and had always been) pointless.
IOW, we don't really need that fallback; all we need in such
cases is to trim O_TRUNC and O_CREAT properly.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/internal.h')
0 files changed, 0 insertions, 0 deletions