fuse: Make shared export state atomic
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>
Hanna Czenczek committed
Mar 9, 2026 at 16:08 UTC
7fe20a2fca4819b43374379ded345b012f699650
1 file changed
+13
-10
block/export/fuse.c
+13
-10
@@ -156,6 +156,7 @@ typedef struct FuseExport {
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/* Whether allow_other was used as a mount option or not */
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bool allow_other;
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+ /* All atomic */
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mode_t st_mode;
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uid_t st_uid;
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gid_t st_gid;
@@ -266,6 +267,7 @@ static int fuse_export_create(BlockExport *blk_exp,
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ERRP_GUARD(); /* ensure clean-up even with error_fatal */
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FuseExport *exp = container_of(blk_exp, FuseExport, common);
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BlockExportOptionsFuse *args = &blk_exp_args->u.fuse;
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+ uint32_t st_mode;
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int ret;
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assert(blk_exp_args->type == BLOCK_EXPORT_TYPE_FUSE);
@@ -334,12 +336,13 @@ static int fuse_export_create(BlockExport *blk_exp,
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args->allow_other = FUSE_EXPORT_ALLOW_OTHER_AUTO;
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}
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- exp->st_mode = S_IFREG | S_IRUSR;
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+ st_mode = S_IFREG | S_IRUSR;
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if (exp->writable) {
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- exp->st_mode |= S_IWUSR;
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+ st_mode |= S_IWUSR;
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}
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- exp->st_uid = getuid();
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- exp->st_gid = getgid();
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+ qatomic_set(&exp->st_mode, st_mode);
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+ qatomic_set(&exp->st_uid, getuid());
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+ qatomic_set(&exp->st_gid, getgid());
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if (args->allow_other == FUSE_EXPORT_ALLOW_OTHER_AUTO) {
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/* Try allow_other == true first, ignore errors */
@@ -817,10 +820,10 @@ fuse_co_getattr(FuseExport *exp, struct fuse_attr_out *out)
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.attr_valid = 1,
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.attr = {
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.ino = 1,
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- .mode = exp->st_mode,
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+ .mode = qatomic_read(&exp->st_mode),
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.nlink = 1,
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- .uid = exp->st_uid,
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- .gid = exp->st_gid,
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+ .uid = qatomic_read(&exp->st_uid),
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+ .gid = qatomic_read(&exp->st_gid),
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.size = length,
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.blksize = blk_bs(exp->common.blk)->bl.request_alignment,
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.blocks = allocated_blocks,
@@ -903,15 +906,15 @@ fuse_co_setattr(FuseExport *exp, struct fuse_attr_out *out, uint32_t to_set,
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if (to_set & FATTR_MODE) {
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/* Ignore FUSE-supplied file type, only change the mode */
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- exp->st_mode = (mode & 07777) | S_IFREG;
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+ qatomic_set(&exp->st_mode, (mode & 07777) | S_IFREG);
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}
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if (to_set & FATTR_UID) {
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- exp->st_uid = uid;
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+ qatomic_set(&exp->st_uid, uid);
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}
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if (to_set & FATTR_GID) {
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- exp->st_gid = gid;
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+ qatomic_set(&exp->st_gid, gid);
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}
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return fuse_co_getattr(exp, out);