block/gluster: glfs_lseek() workaround
On current released versions of glusterfs, glfs_lseek() will sometimes return invalid values for SEEK_DATA or SEEK_HOLE. For SEEK_DATA and SEEK_HOLE, the returned value should be >= the passed offset, or < 0 in the case of error: LSEEK(2): off_t lseek(int fd, off_t offset, int whence); [...] SEEK_HOLE Adjust the file offset to the next hole in the file greater than or equal to offset. If offset points into the middle of a hole, then the file offset is set to offset. If there is no hole past offset, then the file offset is adjusted to the end of the file (i.e., there is an implicit hole at the end of any file). [...] RETURN VALUE Upon successful completion, lseek() returns the resulting offset location as measured in bytes from the beginning of the file. On error, the value (off_t) -1 is returned and errno is set to indicate the error However, occasionally glfs_lseek() for SEEK_HOLE/DATA will return a value less than the passed offset, yet greater than zero. For instance, here are example values observed from this call: offs = glfs_lseek(s->fd, start, SEEK_HOLE); if (offs < 0) { return -errno; /* D1 and (H3 or H4) */ } start == 7608336384 offs == 7607877632 This causes QEMU to abort on the assert test. When this value is returned, errno is also 0. This is a reported and known bug to glusterfs: https://bugzilla.redhat.com/show_bug.cgi?id=1425293 Although this is being fixed in gluster, we still should work around it in QEMU, given that multiple released versions of gluster behave this way. This patch treats the return case of (offs < start) the same as if an error value other than ENXIO is returned; we will assume we learned nothing, and there are no holes in the file. Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Niels de Vos <ndevos@redhat.com> Message-id: 87c0140e9407c08f6e74b04131b610f2e27c014c.1495560397.git.jcody@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
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@ -1275,7 +1275,14 @@ static int find_allocation(BlockDriverState *bs, off_t start,
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if (offs < 0) {
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if (offs < 0) {
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return -errno; /* D3 or D4 */
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return -errno; /* D3 or D4 */
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}
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}
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assert(offs >= start);
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if (offs < start) {
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/* This is not a valid return by lseek(). We are safe to just return
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* -EIO in this case, and we'll treat it like D4. Unfortunately some
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* versions of gluster server will return offs < start, so an assert
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* here will unnecessarily abort QEMU. */
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return -EIO;
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}
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if (offs > start) {
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if (offs > start) {
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/* D2: in hole, next data at offs */
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/* D2: in hole, next data at offs */
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@ -1307,7 +1314,14 @@ static int find_allocation(BlockDriverState *bs, off_t start,
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if (offs < 0) {
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if (offs < 0) {
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return -errno; /* D1 and (H3 or H4) */
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return -errno; /* D1 and (H3 or H4) */
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}
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}
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assert(offs >= start);
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if (offs < start) {
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/* This is not a valid return by lseek(). We are safe to just return
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* -EIO in this case, and we'll treat it like H4. Unfortunately some
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* versions of gluster server will return offs < start, so an assert
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* here will unnecessarily abort QEMU. */
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return -EIO;
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}
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if (offs > start) {
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if (offs > start) {
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/*
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/*
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