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b=aMsawhgh9BwqrryYqi+W+63jCO /Uuz/A7YCu8QXbC/ErbOjU6LOwABRhf3q5lgdCSt0GA2xwcjXHUjz6f6lzEnVkGBMK/R08zXRR4Yh fikqIljLdNfWREWEJAb7ekS2vjlWfgzgH1ACqZI+/oEkmi9sb8e+o7ft8vgMyRAtW/BiicIJa1xa9 8LPsI6nhMxZqyT4frifavmMcSGJkP6k68sldjPM+BCKrRwP2OG6Xt132Fw3K5rfqu8Pd8s4y2XGpg DGqdbiTbqwgH4uuR8BCZHo3K2Tjhi0b3IhKmMlP0sV2IIYNvViOgWQ/PTvnB5FCLeTqV12GBPlV1I u9GRaM+w==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.99 #2 (Red Hat Linux)) id 1vUcor-00000001yMh-3YW7; Sun, 14 Dec 2025 03:30:49 +0000 Date: Sun, 14 Dec 2025 03:30:49 +0000 From: Al Viro To: Hugh Dickins Cc: Miklos Szeredi , Christian Brauner , Andrew Morton , Baolin Wang , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Chuck Lever Subject: [RFC][PATCH 2/2] shmem: fix recovery on rename failures Message-ID: <20251214033049.GB460900@ZenIV> References: <47e9d03c-7a50-2c7d-247d-36f95a5329ed@google.com> <20251212050225.GD1712166@ZenIV> <20251212053452.GE1712166@ZenIV> <8ab63110-38b2-2188-91c5-909addfc9b23@google.com> <20251212063026.GF1712166@ZenIV> <2a102c6d-82d9-2751-cd31-c836b5c739b7@google.com> <20251213072241.GH1712166@ZenIV> <20251214032734.GL1712166@ZenIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251214032734.GL1712166@ZenIV> X-Rspam-User: X-Rspamd-Queue-Id: 5C3D340009 X-Rspamd-Server: rspam10 X-Stat-Signature: xddczoqkkge7bc83kbsng3r5sy3p8zc6 X-HE-Tag: 1765683018-865233 X-HE-Meta: U2FsdGVkX1++qCTEmH7qGQlqdJq0CEfZoBvTkQjCs96zNhmJEHt9JaXWAgO999ZKx25kiG4bWh22GWDUNMoQj+I6TUa+r9Zv9D/Zp9NhHldVXouCPoGFES3NiVGdCjYOgwLkI+jOeo367QxQKXB/DAffLVldL09EtOxLO/CiDCipJHPHSGgmH6kCdHz56uRVryG6Tgc+J0i/AVWOE8/tWDCvV3Hy1iToybknw1ESG4YEPTkL7986SSRFKJ8Uh+Q6R78wpDt8wQGWEDNg4QoWX4zZS752ytF2v2FKeL2Cbo1ZOZ0Vm5W4CUhPqgySPA8kWUm0IwvHfPxAZjOxbRj1aL7l9f8EzoIYO81urE9qoMVkUX8bmtEOK8t8TIeFM97CCEuwbcDDJNOjYWss48/GnSJa1EeRPAHHFD95Y4rEEVpYiafHIiiOyiW+6EeZuq8I6ryfxn1XNkd9N00oly7I9e1TaIdg0yV7ME1wIG+Eq1vhji58RG9O/PQpTA34iauMnAsuadBi6ENKGLbe3TPRcp/joOKYdqRam6wqbqA+ivNLW7R4a91MWyMoqEUA+UQfp2GnKsZ316XCYQ440oqM5leMVH+BMhrqvMBrZ8hFvdUXAb21oreTjzSV9g+fpq1ur6Gdf7I2QQXtlxypKyYpZQr99pXlr+7D/WU/j3GLqnAzMJcPKLVHNicRNHNN1z/DIMwHtuKmdzHdKoD3WpLiYAsekyNGfjkkRYCOOFaJyAwoSnf8mAAF4jtRw/NHejZINv8uX0BV46+ZJhmRaM0ljhtUgT8I0B9IBFZgyM8wQLnColI4ZTMxg6AXRxLoxb/9SGnCAd8GfXXXU4bEQ3HBX9P18D+U34GV1+0tK7TverK10KCxxd2fkdN3yiL0HKhPVdtPGQjJjWlVwA4SatvzvNg7kKpZAMi131IRmDJV2dPJN6Li9uKgET4FhOpqNcyANKGH+9sjJCXtPjURCBS qDP/nlHj 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: maple_tree insertions can fail if we are seriously short on memory; simple_offset_rename() does not recover well if it runs into that. The same goes for simple_offset_rename_exchange(). Moreover, shmem_whiteout() expects that if it succeeds, the caller will progress to d_move(), i.e. that shmem_rename2() won't fail past the successful call of shmem_whiteout(). Not hard to fix, fortunately - mtree_store() can't fail if the index we are trying to store into is already present in the tree as a singleton. For simple_offset_rename_exchange() that's enough - we just need to be careful about the order of operations. For simple_offset_rename() solution is to preinsert the target into the tree for new_dir; the rest can be done without any potentially failing operations. That preinsertion has to be done in shmem_rename2() rather than in simple_offset_rename() itself - otherwise we'd need to deal with the possibility of failure after successful shmem_whiteout(). Fixes: a2e459555c5f ("shmem: stable directory offsets") Signed-off-by: Al Viro --- fs/libfs.c | 50 +++++++++++++++++++--------------------------- include/linux/fs.h | 2 +- mm/shmem.c | 18 ++++++++++++----- 3 files changed, 35 insertions(+), 35 deletions(-) diff --git a/fs/libfs.c b/fs/libfs.c index 9264523be85c..591eb649ebba 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -346,22 +346,22 @@ void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry) * User space expects the directory offset value of the replaced * (new) directory entry to be unchanged after a rename. * - * Returns zero on success, a negative errno value on failure. + * Caller must have grabbed a slot for new_dentry in the maple_tree + * associated with new_dir, even if dentry is negative. */ -int simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry, - struct inode *new_dir, struct dentry *new_dentry) +void simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry) { struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir); struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir); long new_offset = dentry2offset(new_dentry); - simple_offset_remove(old_ctx, old_dentry); + if (WARN_ON(!new_offset)) + return; - if (new_offset) { - offset_set(new_dentry, 0); - return simple_offset_replace(new_ctx, old_dentry, new_offset); - } - return simple_offset_add(new_ctx, old_dentry); + simple_offset_remove(old_ctx, old_dentry); + offset_set(new_dentry, 0); + WARN_ON(simple_offset_replace(new_ctx, old_dentry, new_offset)); } /** @@ -388,31 +388,23 @@ int simple_offset_rename_exchange(struct inode *old_dir, long new_index = dentry2offset(new_dentry); int ret; - simple_offset_remove(old_ctx, old_dentry); - simple_offset_remove(new_ctx, new_dentry); + if (WARN_ON(!old_index || !new_index)) + return -EINVAL; - ret = simple_offset_replace(new_ctx, old_dentry, new_index); - if (ret) - goto out_restore; + ret = mtree_store(&new_ctx->mt, new_index, old_dentry, GFP_KERNEL); + if (WARN_ON(ret)) + return ret; - ret = simple_offset_replace(old_ctx, new_dentry, old_index); - if (ret) { - simple_offset_remove(new_ctx, old_dentry); - goto out_restore; + ret = mtree_store(&old_ctx->mt, old_index, new_dentry, GFP_KERNEL); + if (WARN_ON(ret)) { + mtree_store(&new_ctx->mt, new_index, new_dentry, GFP_KERNEL); + return ret; } - ret = simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry); - if (ret) { - simple_offset_remove(new_ctx, old_dentry); - simple_offset_remove(old_ctx, new_dentry); - goto out_restore; - } + offset_set(old_dentry, new_index); + offset_set(new_dentry, old_index); + simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry); return 0; - -out_restore: - (void)simple_offset_replace(old_ctx, old_dentry, old_index); - (void)simple_offset_replace(new_ctx, new_dentry, new_index); - return ret; } /** diff --git a/include/linux/fs.h b/include/linux/fs.h index 04ceeca12a0d..f5c9cf28c4dc 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3247,7 +3247,7 @@ struct offset_ctx { void simple_offset_init(struct offset_ctx *octx); int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry); void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry); -int simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry, +void simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry); int simple_offset_rename_exchange(struct inode *old_dir, struct dentry *old_dentry, diff --git a/mm/shmem.c b/mm/shmem.c index d3edc809e2e7..4232f8a39a43 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -4039,6 +4039,7 @@ static int shmem_rename2(struct mnt_idmap *idmap, struct inode *inode = d_inode(old_dentry); int they_are_dirs = S_ISDIR(inode->i_mode); int error; + int had_offset = false; if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT)) return -EINVAL; @@ -4050,16 +4051,23 @@ static int shmem_rename2(struct mnt_idmap *idmap, if (!simple_empty(new_dentry)) return -ENOTEMPTY; + error = simple_offset_add(shmem_get_offset_ctx(new_dir), new_dentry); + if (error == -EBUSY) + had_offset = true; + else if (unlikely(error)) + return error; + if (flags & RENAME_WHITEOUT) { error = shmem_whiteout(idmap, old_dir, old_dentry); - if (error) + if (error) { + if (!had_offset) + simple_offset_remove(shmem_get_offset_ctx(new_dir), + new_dentry); return error; + } } - error = simple_offset_rename(old_dir, old_dentry, new_dir, new_dentry); - if (error) - return error; - + simple_offset_rename(old_dir, old_dentry, new_dir, new_dentry); if (d_really_is_positive(new_dentry)) { (void) shmem_unlink(new_dir, new_dentry); if (they_are_dirs) { -- 2.47.3