On 2/12/25 9:16 PM, Mikhail Gavrilov wrote: > Hi, > I spotted that Google Chrome started working without HW acceleration. > And git bisect found commit b9b588f22a0c049a14885399e27625635ae6ef91 > Author: Chuck Lever <chuck.lever@xxxxxxxxxx> > Date: Sat Dec 28 12:55:21 2024 -0500 > > libfs: Use d_children list to iterate simple_offset directories > > The mtree mechanism has been effective at creating directory offsets > that are stable over multiple opendir instances. However, it has not > been able to handle the subtleties of renames that are concurrent > with readdir. > > Instead of using the mtree to emit entries in the order of their > offset values, use it only to map incoming ctx->pos to a starting > entry. Then use the directory's d_children list, which is already > maintained properly by the dcache, to find the next child to emit. > > One of the sneaky things about this is that when the mtree-allocated > offset value wraps (which is very rare), looking up ctx->pos++ is > not going to find the next entry; it will return NULL. Instead, by > following the d_children list, the offset values can appear in any > order but all of the entries in the directory will be visited > eventually. > > Note also that the readdir() is guaranteed to reach the tail of this > list. Entries are added only at the head of d_children, and readdir > walks from its current position in that list towards its tail. > > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> > Link: https://lore.kernel.org/r/20241228175522.1854234-6-cel@xxxxxxxxxx > Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> > > fs/libfs.c | 84 > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------------------- > 1 file changed, 58 insertions(+), 26 deletions(-) > > I tested Google Chrome after reverting commit b9b588f22a0c and ensured > that this fixed the issue. I need a simpler reproducer, please. "Chrome stopped working" doesn't give me anything actionable. > Machine spec: https://linux-hardware.org/?probe=5810cda90d > I attached below my build config. > > Chuck, you, as the author problem commit, can look into this, please? -- Chuck Lever
