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fuse: Make shared export state atomic

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The next commit is going to allow multi-threaded access to a FUSE
export.  In order to allow safe concurrent SETATTR operations that
can modify the shared st_mode, st_uid, and st_gid, make any access to
those fields atomic operations.

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20260309150856.26800-23-hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Hanna Czenczek
2026-03-09 16:08:53 +01:00
committed by Kevin Wolf
parent 1a08957704
commit 7fe20a2fca
1 changed files with 13 additions and 10 deletions
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23
block/export/fuse.c
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@@ -156,6 +156,7 @@ typedef struct FuseExport {
/* Whether allow_other was used as a mount option or not */
bool allow_other;
/* All atomic */
mode_t st_mode;
uid_t st_uid;
gid_t st_gid;
@@ -266,6 +267,7 @@ static int fuse_export_create(BlockExport *blk_exp,
ERRP_GUARD(); /* ensure clean-up even with error_fatal */
FuseExport *exp = container_of(blk_exp, FuseExport, common);
BlockExportOptionsFuse *args = &blk_exp_args->u.fuse;
uint32_t st_mode;
int ret;
assert(blk_exp_args->type == BLOCK_EXPORT_TYPE_FUSE);
@@ -334,12 +336,13 @@ static int fuse_export_create(BlockExport *blk_exp,
args->allow_other = FUSE_EXPORT_ALLOW_OTHER_AUTO;
}
exp->st_mode = S_IFREG | S_IRUSR;
st_mode = S_IFREG | S_IRUSR;
if (exp->writable) {
exp->st_mode |= S_IWUSR;
st_mode |= S_IWUSR;
}
exp->st_uid = getuid();
exp->st_gid = getgid();
qatomic_set(&exp->st_mode, st_mode);
qatomic_set(&exp->st_uid, getuid());
qatomic_set(&exp->st_gid, getgid());
if (args->allow_other == FUSE_EXPORT_ALLOW_OTHER_AUTO) {
/* Try allow_other == true first, ignore errors */
@@ -817,10 +820,10 @@ fuse_co_getattr(FuseExport *exp, struct fuse_attr_out *out)
.attr_valid = 1,
.attr = {
.ino = 1,
.mode = exp->st_mode,
.mode = qatomic_read(&exp->st_mode),
.nlink = 1,
.uid = exp->st_uid,
.gid = exp->st_gid,
.uid = qatomic_read(&exp->st_uid),
.gid = qatomic_read(&exp->st_gid),
.size = length,
.blksize = blk_bs(exp->common.blk)->bl.request_alignment,
.blocks = allocated_blocks,
@@ -903,15 +906,15 @@ fuse_co_setattr(FuseExport *exp, struct fuse_attr_out *out, uint32_t to_set,
if (to_set & FATTR_MODE) {
/* Ignore FUSE-supplied file type, only change the mode */
exp->st_mode = (mode & 07777) | S_IFREG;
qatomic_set(&exp->st_mode, (mode & 07777) | S_IFREG);
}
if (to_set & FATTR_UID) {
exp->st_uid = uid;
qatomic_set(&exp->st_uid, uid);
}
if (to_set & FATTR_GID) {
exp->st_gid = gid;
qatomic_set(&exp->st_gid, gid);
}
return fuse_co_getattr(exp, out);