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Handle the case of posix_fadvise() returning ENOENT
This commit is contained in:
Andrea Mazzoleni
parent
de598080c4
commit
35b5c46851
4 changed files with 81 additions and 9 deletions
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@ -49,7 +49,7 @@ STREAM* sopen_read(const char* file, int flags)
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#if HAVE_POSIX_FADVISE
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if (s->flags & STREAM_FLAGS_SEQUENTIAL) {
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/* advise sequential access */
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ret = posix_fadvise(s->handle[0].f, 0, 0, POSIX_FADV_SEQUENTIAL);
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ret = posix_fadvise_wrapper(s->handle[0].f, 0, 0, POSIX_FADV_SEQUENTIAL);
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if (ret == ENOSYS) {
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log_error(errno, "WARNING! fadvise() is not supported in this platform. Performance may not be optimal!\n");
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/* call is not supported, like in armhf, see posix_fadvise manpage */
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@ -137,7 +137,7 @@ int sopen_multi_file(STREAM* s, unsigned i, const char* file)
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#if HAVE_POSIX_FADVISE
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if (s->flags & STREAM_FLAGS_SEQUENTIAL) {
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/* advise sequential access */
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ret = posix_fadvise(f, 0, 0, POSIX_FADV_SEQUENTIAL);
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ret = posix_fadvise_wrapper(f, 0, 0, POSIX_FADV_SEQUENTIAL);
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if (ret == ENOSYS) {
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/* call is not supported, like in armhf, see posix_fadvise manpage */
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ret = 0;
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@ -1357,7 +1357,7 @@ int advise_open(struct advise_struct* advise, int f)
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/* advise noreuse access, this avoids to pollute the page cache */
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/* supported from Linux Kernel 6.3 with this commit: https://github.com/torvalds/linux/commit/17e810229cb3068b692fa078bd9b3a6527e0866a */
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ret = posix_fadvise(f, 0, 0, POSIX_FADV_NOREUSE);
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ret = posix_fadvise_wrapper(f, 0, 0, POSIX_FADV_NOREUSE);
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if (ret == ENOSYS) {
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/* call is not supported */
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ret = 0;
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@ -1370,7 +1370,7 @@ int advise_open(struct advise_struct* advise, int f)
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}
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/* advise sequential access, this doubles the read-ahead window size */
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ret = posix_fadvise(f, 0, 0, POSIX_FADV_SEQUENTIAL);
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ret = posix_fadvise_wrapper(f, 0, 0, POSIX_FADV_SEQUENTIAL);
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if (ret == ENOSYS) {
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/* call is not supported, like in armhf, see posix_fadvise manpage */
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ret = 0;
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@ -1550,8 +1550,11 @@ int advise_write(struct advise_struct* advise, int f, data_off_t offset, data_of
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}
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/* flush the data from the cache */
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ret = posix_fadvise(f, discard_offset, discard_size, POSIX_FADV_DONTNEED);
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/* for POSIX_FADV_DONTNEED we don't allow failure with ENOSYS */
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ret = posix_fadvise_wrapper(f, discard_offset, discard_size, POSIX_FADV_DONTNEED);
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if (ret == ENOSYS) {
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/* call is not supported */
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ret = 0;
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}
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if (ret != 0) {
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/* LCOV_EXCL_START */
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errno = ret; /* posix_fadvise return the error code */
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@ -1578,8 +1581,11 @@ int advise_read(struct advise_struct* advise, int f, data_off_t offset, data_off
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int ret;
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/* flush the data from the cache */
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ret = posix_fadvise(f, offset, size, POSIX_FADV_DONTNEED);
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/* for POSIX_FADV_DONTNEED we don't allow failure with ENOSYS */
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ret = posix_fadvise_wrapper(f, offset, size, POSIX_FADV_DONTNEED);
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if (ret == ENOSYS) {
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/* call is not supported */
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ret = 0;
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}
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if (ret != 0) {
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/* LCOV_EXCL_START */
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errno = ret; /* posix_fadvise return the error code */
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@ -14,6 +14,63 @@ int exit_success = 0;
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int exit_failure = 1;
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int exit_sync_needed = 2;
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#if HAVE_POSIX_FADVISE
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/**
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* Wrapper around posix_fadvise() that handles ENOENT by converting it to
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* ENOSYS.
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*
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* Why can posix_fadvise() return ENOENT?
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*
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* According to POSIX and the Linux kernel's standard fadvise64 implementation
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* (mm/fadvise.c), posix_fadvise() should only return EBADF (bad file
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* descriptor), ESPIPE (fd refers to a pipe or FIFO), or EINVAL (invalid
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* advice value or arguments). ENOENT is never generated by the kernel's
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* generic path.
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*
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* However, the VFS layer allows individual filesystems to provide their own
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* .fadvise() method, which is called instead of (or in addition to) the
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* generic implementation. Certain filesystem drivers can return ENOENT in
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* this method for reasons that are completely unrelated to the file not
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* existing (the file is clearly open, we have a valid fd):
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*
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* - NFS: A stale NFS inode can be revalidated against the server while
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* fadvise is being processed. If the server-side file has been removed or
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* renamed, the revalidation discovers the inode is gone and returns
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* -ENOENT, even though the client still holds an open file descriptor.
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*
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* - FUSE-based filesystems (mergerfs, sshfs, rclone, etc.): The FUSE daemon
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* receives the fadvise request and may forward it to an underlying backend.
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* If that backend cannot find the file (e.g., the backing path has changed,
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* the FUSE daemon is partially initialised, or the daemon translates the
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* request and the target layer returns an error), the daemon may return
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* ENOENT to the kernel.
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*
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* - Overlayfs (used by Docker, Podman, LXC): The overlayfs .fadvise()
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* implementation delegates to the lower or upper layer. If the lookup
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* through the overlay stack fails to find the real inode (e.g., the upper
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* directory entry is absent and the lower copy is in a weird state), the
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* delegation can return ENOENT.
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*
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* - Other network or virtual filesystems: Any out-of-tree or in-tree
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* filesystem that implements .fadvise() and performs a path or inode
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* lookup as part of processing the hint can propagate ENOENT if that
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* internal lookup fails.
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*
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* Because posix_fadvise() is always an advisory hint, it never affects
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* correctness, only performance, it is safe to treat unexpected errors,
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* including ENOENT, as "not supported" (ENOSYS) and continue.
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*/
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int posix_fadvise_wrapper(int fd, off_t offset, off_t len, int advice)
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{
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int ret = posix_fadvise(fd, offset, len, advice);
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if (ret == ENOENT)
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return ENOSYS;
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return ret;
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}
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#endif
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int open_noatime(const char* file, int flags)
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{
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#ifdef O_NOATIME
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@ -2054,7 +2111,11 @@ static int devup(dev_t device, const char* name)
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#if HAVE_POSIX_FADVISE
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/* clear cache */
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ret = posix_fadvise(f, offset, 4096, POSIX_FADV_DONTNEED);
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ret = posix_fadvise_wrapper(f, offset, 4096, POSIX_FADV_DONTNEED);
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if (ret == ENOSYS) {
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/* call is not supported */
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ret = 0;
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}
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if (ret != 0) {
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/* LCOV_EXCL_START */
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close(f);
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@ -12,6 +12,11 @@
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#define O_BINARY 0 /**< Not used in Unix. */
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#define O_SEQUENTIAL 0 /**< In Unix posix_fadvise() shall be used. */
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#if HAVE_POSIX_FADVISE
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int posix_fadvise_wrapper(int fd, off_t offset, off_t len, int advice);
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#endif
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/**
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* If nanoseconds are not supported, we report the special STAT_NSEC_INVALID value,
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* to mark that it's undefined.
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