git_open(): untangle possible NOATIME and CLOEXEC interactions
The way we structured the fallback/retry mechanism for opening with O_NOATIME and O_CLOEXEC meant that if we failed due to lack of support to open the file with O_NOATIME option (i.e. EINVAL), we would still try to drop O_CLOEXEC first and retry, and then drop O_NOATIME. A platform on which O_NOATIME is defined in the header without support from the kernel wouldn't have a chance to open with O_CLOEXEC option due to this code structure. Arguably, O_CLOEXEC is more important than O_NOATIME, as the latter is mostly about performance, while the former can affect correctness. Instead use O_CLOEXEC to open the file, and then use fcntl(2) to set O_NOATIME on the resulting file descriptor. open(2) itself does not cause atime to be updated according to Linus [*1*]. The helper to do the former can be usable in the codepath in ce_compare_data() that was recently added to open a file descriptor with O_CLOEXEC; use it while we are at it. *1* <CA+55aFw83E+zOd+z5h-CA-3NhrLjVr-anL6pubrSWttYx3zu8g@mail.gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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cache.h
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cache.h
@ -1122,6 +1122,7 @@ extern int write_sha1_file(const void *buf, unsigned long len, const char *type,
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extern int hash_sha1_file_literally(const void *buf, unsigned long len, const char *type, unsigned char *sha1, unsigned flags);
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extern int pretend_sha1_file(void *, unsigned long, enum object_type, unsigned char *);
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extern int force_object_loose(const unsigned char *sha1, time_t mtime);
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extern int git_open_cloexec(const char *name, int flags);
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extern int git_open(const char *name);
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extern void *map_sha1_file(const unsigned char *sha1, unsigned long *size);
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extern int unpack_sha1_header(git_zstream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz);
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