Merge remote-tracking branch 'mreitz/block' into queue-block
* mreitz/block: raw-posix: The SEEK_HOLE code is flawed, rewrite it raw-posix: SEEK_HOLE suffices, get rid of FIEMAP raw-posix: Fix comment for raw_co_get_block_status()
This commit is contained in:
Kevin Wolf
commit
8676785302
@ -60,9 +60,6 @@
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#define FS_NOCOW_FL 0x00800000 /* Do not cow file */
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#endif
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#endif
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#ifdef CONFIG_FIEMAP
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#include <linux/fiemap.h>
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#endif
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#ifdef CONFIG_FALLOCATE_PUNCH_HOLE
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#include <linux/falloc.h>
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#endif
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@ -151,9 +148,6 @@ typedef struct BDRVRawState {
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bool has_write_zeroes:1;
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bool discard_zeroes:1;
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bool needs_alignment;
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#ifdef CONFIG_FIEMAP
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bool skip_fiemap;
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#endif
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} BDRVRawState;
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typedef struct BDRVRawReopenState {
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@ -1481,83 +1475,93 @@ out:
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return result;
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}
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static int try_fiemap(BlockDriverState *bs, off_t start, off_t *data,
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off_t *hole, int nb_sectors)
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{
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#ifdef CONFIG_FIEMAP
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BDRVRawState *s = bs->opaque;
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int ret = 0;
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struct {
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struct fiemap fm;
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struct fiemap_extent fe;
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} f;
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if (s->skip_fiemap) {
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return -ENOTSUP;
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}
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f.fm.fm_start = start;
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f.fm.fm_length = (int64_t)nb_sectors * BDRV_SECTOR_SIZE;
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f.fm.fm_flags = FIEMAP_FLAG_SYNC;
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f.fm.fm_extent_count = 1;
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f.fm.fm_reserved = 0;
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if (ioctl(s->fd, FS_IOC_FIEMAP, &f) == -1) {
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s->skip_fiemap = true;
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return -errno;
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}
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if (f.fm.fm_mapped_extents == 0) {
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/* No extents found, data is beyond f.fm.fm_start + f.fm.fm_length.
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* f.fm.fm_start + f.fm.fm_length must be clamped to the file size!
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*/
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off_t length = lseek(s->fd, 0, SEEK_END);
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*hole = f.fm.fm_start;
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*data = MIN(f.fm.fm_start + f.fm.fm_length, length);
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} else {
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*data = f.fe.fe_logical;
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*hole = f.fe.fe_logical + f.fe.fe_length;
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if (f.fe.fe_flags & FIEMAP_EXTENT_UNWRITTEN) {
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ret |= BDRV_BLOCK_ZERO;
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}
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}
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return ret;
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#else
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return -ENOTSUP;
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#endif
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}
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static int try_seek_hole(BlockDriverState *bs, off_t start, off_t *data,
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off_t *hole)
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/*
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* Find allocation range in @bs around offset @start.
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* May change underlying file descriptor's file offset.
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* If @start is not in a hole, store @start in @data, and the
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* beginning of the next hole in @hole, and return 0.
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* If @start is in a non-trailing hole, store @start in @hole and the
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* beginning of the next non-hole in @data, and return 0.
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* If @start is in a trailing hole or beyond EOF, return -ENXIO.
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* If we can't find out, return a negative errno other than -ENXIO.
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*/
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static int find_allocation(BlockDriverState *bs, off_t start,
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off_t *data, off_t *hole)
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{
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#if defined SEEK_HOLE && defined SEEK_DATA
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BDRVRawState *s = bs->opaque;
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off_t offs;
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*hole = lseek(s->fd, start, SEEK_HOLE);
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if (*hole == -1) {
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return -errno;
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/*
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* SEEK_DATA cases:
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* D1. offs == start: start is in data
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* D2. offs > start: start is in a hole, next data at offs
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* D3. offs < 0, errno = ENXIO: either start is in a trailing hole
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* or start is beyond EOF
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* If the latter happens, the file has been truncated behind
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* our back since we opened it. All bets are off then.
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* Treating like a trailing hole is simplest.
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* D4. offs < 0, errno != ENXIO: we learned nothing
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*/
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offs = lseek(s->fd, start, SEEK_DATA);
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if (offs < 0) {
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return -errno; /* D3 or D4 */
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}
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assert(offs >= start);
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if (offs > start) {
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/* D2: in hole, next data at offs */
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*hole = start;
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*data = offs;
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return 0;
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}
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if (*hole > start) {
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/* D1: in data, end not yet known */
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/*
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* SEEK_HOLE cases:
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* H1. offs == start: start is in a hole
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* If this happens here, a hole has been dug behind our back
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* since the previous lseek().
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* H2. offs > start: either start is in data, next hole at offs,
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* or start is in trailing hole, EOF at offs
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* Linux treats trailing holes like any other hole: offs ==
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* start. Solaris seeks to EOF instead: offs > start (blech).
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* If that happens here, a hole has been dug behind our back
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* since the previous lseek().
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* H3. offs < 0, errno = ENXIO: start is beyond EOF
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* If this happens, the file has been truncated behind our
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* back since we opened it. Treat it like a trailing hole.
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* H4. offs < 0, errno != ENXIO: we learned nothing
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* Pretend we know nothing at all, i.e. "forget" about D1.
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*/
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offs = lseek(s->fd, start, SEEK_HOLE);
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if (offs < 0) {
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return -errno; /* D1 and (H3 or H4) */
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}
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assert(offs >= start);
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if (offs > start) {
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/*
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* D1 and H2: either in data, next hole at offs, or it was in
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* data but is now in a trailing hole. In the latter case,
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* all bets are off. Treating it as if it there was data all
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* the way to EOF is safe, so simply do that.
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*/
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*data = start;
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} else {
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/* On a hole. We need another syscall to find its end. */
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*data = lseek(s->fd, start, SEEK_DATA);
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if (*data == -1) {
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*data = lseek(s->fd, 0, SEEK_END);
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}
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*hole = offs;
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return 0;
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}
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return 0;
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/* D1 and H1 */
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return -EBUSY;
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#else
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return -ENOTSUP;
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#endif
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}
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/*
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* Returns true iff the specified sector is present in the disk image. Drivers
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* not implementing the functionality are assumed to not support backing files,
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* hence all their sectors are reported as allocated.
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* Returns the allocation status of the specified sectors.
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*
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* If 'sector_num' is beyond the end of the disk image the return value is 0
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* and 'pnum' is set to 0.
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@ -1593,28 +1597,26 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
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nb_sectors = DIV_ROUND_UP(total_size - start, BDRV_SECTOR_SIZE);
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}
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ret = try_seek_hole(bs, start, &data, &hole);
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if (ret < 0) {
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ret = try_fiemap(bs, start, &data, &hole, nb_sectors);
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if (ret < 0) {
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/* Assume everything is allocated. */
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data = 0;
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hole = start + nb_sectors * BDRV_SECTOR_SIZE;
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ret = 0;
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}
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}
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assert(ret >= 0);
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if (data <= start) {
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ret = find_allocation(bs, start, &data, &hole);
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if (ret == -ENXIO) {
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/* Trailing hole */
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*pnum = nb_sectors;
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ret = BDRV_BLOCK_ZERO;
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} else if (ret < 0) {
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/* No info available, so pretend there are no holes */
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*pnum = nb_sectors;
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ret = BDRV_BLOCK_DATA;
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} else if (data == start) {
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/* On a data extent, compute sectors to the end of the extent. */
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*pnum = MIN(nb_sectors, (hole - start) / BDRV_SECTOR_SIZE);
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return ret | BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start;
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ret = BDRV_BLOCK_DATA;
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} else {
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/* On a hole, compute sectors to the beginning of the next extent. */
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assert(hole == start);
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*pnum = MIN(nb_sectors, (data - start) / BDRV_SECTOR_SIZE);
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return ret | BDRV_BLOCK_ZERO | BDRV_BLOCK_OFFSET_VALID | start;
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ret = BDRV_BLOCK_ZERO;
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}
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return ret | BDRV_BLOCK_OFFSET_VALID | start;
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}
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static coroutine_fn BlockAIOCB *raw_aio_discard(BlockDriverState *bs,
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