Commit 22afa7b5b67bb8bc58939d100363ee6753a50467
Committed by
Anthony Liguori
Anthony Liguori
1 parent
ae95ade0
block-raw: Allow pread beyond the end of growable images
When using O_DIRECT, qcow2 snapshots didn't work any more for me. In the process of creating the snapshot, qcow2 tries to pwrite some new information (e.g. new L1 table) which will often end up being after the old end of the image file. Now pwrite tries to align things and reads the old contents of the file, read returns 0 because there is nothing to read after the end of file and pwrite is stuck in an endless loop. This patch allows to pread beyond the end of an image file. Whenever the given offset is after the end of the image file, the read succeeds and fills the buffer with zeros. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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block/raw-posix.c
| @@ -117,6 +117,7 @@ typedef struct BDRVRawState { | @@ -117,6 +117,7 @@ typedef struct BDRVRawState { | ||
| 117 | static int posix_aio_init(void); | 117 | static int posix_aio_init(void); |
| 118 | 118 | ||
| 119 | static int fd_open(BlockDriverState *bs); | 119 | static int fd_open(BlockDriverState *bs); |
| 120 | +static int64_t raw_getlength(BlockDriverState *bs); | ||
| 120 | 121 | ||
| 121 | #if defined(__FreeBSD__) | 122 | #if defined(__FreeBSD__) |
| 122 | static int cdrom_reopen(BlockDriverState *bs); | 123 | static int cdrom_reopen(BlockDriverState *bs); |
| @@ -231,6 +232,16 @@ static int raw_pread_aligned(BlockDriverState *bs, int64_t offset, | @@ -231,6 +232,16 @@ static int raw_pread_aligned(BlockDriverState *bs, int64_t offset, | ||
| 231 | if (ret == count) | 232 | if (ret == count) |
| 232 | goto label__raw_read__success; | 233 | goto label__raw_read__success; |
| 233 | 234 | ||
| 235 | + /* Allow reads beyond the end (needed for pwrite) */ | ||
| 236 | + if ((ret == 0) && bs->growable) { | ||
| 237 | + int64_t size = raw_getlength(bs); | ||
| 238 | + if (offset >= size) { | ||
| 239 | + memset(buf, 0, count); | ||
| 240 | + ret = count; | ||
| 241 | + goto label__raw_read__success; | ||
| 242 | + } | ||
| 243 | + } | ||
| 244 | + | ||
| 234 | DEBUG_BLOCK_PRINT("raw_pread(%d:%s, %" PRId64 ", %p, %d) [%" PRId64 | 245 | DEBUG_BLOCK_PRINT("raw_pread(%d:%s, %" PRId64 ", %p, %d) [%" PRId64 |
| 235 | "] read failed %d : %d = %s\n", | 246 | "] read failed %d : %d = %s\n", |
| 236 | s->fd, bs->filename, offset, buf, count, | 247 | s->fd, bs->filename, offset, buf, count, |