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fuse: (Partially) implement fallocate() 

This allows allocating areas after the (old) EOF as part of a growing
resize, writing zeroes, and discarding.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20201027190600.192171-6-mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
master
Max Reitz 2020-10-27 20:05:45 +01:00 committed by Kevin Wolf
parent 4fba06d594
commit 4ca37a96a7
1 changed files with 84 additions and 0 deletions
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84
block/export/fuse.c
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@ -521,6 +521,89 @@ static void fuse_write(fuse_req_t req, fuse_ino_t inode, const char *buf,
}
}
/**
* Let clients perform various fallocate() operations.
*/
static void fuse_fallocate(fuse_req_t req, fuse_ino_t inode, int mode,
off_t offset, off_t length,
struct fuse_file_info *fi)
{
FuseExport *exp = fuse_req_userdata(req);
int64_t blk_len;
int ret;
if (!exp->writable) {
fuse_reply_err(req, EACCES);
return;
}
blk_len = blk_getlength(exp->common.blk);
if (blk_len < 0) {
fuse_reply_err(req, -blk_len);
return;
}
if (mode & FALLOC_FL_KEEP_SIZE) {
length = MIN(length, blk_len - offset);
}
if (mode & FALLOC_FL_PUNCH_HOLE) {
if (!(mode & FALLOC_FL_KEEP_SIZE)) {
fuse_reply_err(req, EINVAL);
return;
}
do {
int size = MIN(length, BDRV_REQUEST_MAX_BYTES);
ret = blk_pdiscard(exp->common.blk, offset, size);
offset += size;
length -= size;
} while (ret == 0 && length > 0);
} else if (mode & FALLOC_FL_ZERO_RANGE) {
if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + length > blk_len) {
/* No need for zeroes, we are going to write them ourselves */
ret = fuse_do_truncate(exp, offset + length, false,
PREALLOC_MODE_OFF);
if (ret < 0) {
fuse_reply_err(req, -ret);
return;
}
}
do {
int size = MIN(length, BDRV_REQUEST_MAX_BYTES);
ret = blk_pwrite_zeroes(exp->common.blk,
offset, size, 0);
offset += size;
length -= size;
} while (ret == 0 && length > 0);
} else if (!mode) {
/* We can only fallocate at the EOF with a truncate */
if (offset < blk_len) {
fuse_reply_err(req, EOPNOTSUPP);
return;
}
if (offset > blk_len) {
/* No preallocation needed here */
ret = fuse_do_truncate(exp, offset, true, PREALLOC_MODE_OFF);
if (ret < 0) {
fuse_reply_err(req, -ret);
return;
}
}
ret = fuse_do_truncate(exp, offset + length, true,
PREALLOC_MODE_FALLOC);
} else {
ret = -EOPNOTSUPP;
}
fuse_reply_err(req, ret < 0 ? -ret : 0);
}
/**
* Let clients fsync the exported image.
*/
@ -552,6 +635,7 @@ static const struct fuse_lowlevel_ops fuse_ops = {
.open = fuse_open,
.read = fuse_read,
.write = fuse_write,
.fallocate = fuse_fallocate,
.flush = fuse_flush,
.fsync = fuse_fsync,
};